Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$186.55	10.259%	$205.6882	$205.69	$205.70	$205.70
Purchase #2	$135.75	10.381%	$149.8422	$149.84	$149.85	$149.80
Purchase #3	$155.49	5.726%	$164.3934	$164.39	$164.40	$164.40
Purchase #4	$245.56	7.698%	$264.4632	$264.46	$264.45	$264.50
Purchase #5	$110.83	11.257%	$123.3061	$123.31	$123.30	$123.30
Purchase #6	$184.81	13.656%	$210.0477	$210.05	$210.05	$210.00
Purchase #7	$127.57	13.282%	$144.5138	$144.51	$144.50	$144.50
7 purchase totals =	$1,146.56		$1,262.2546	$1,262.25	$1,262.25	$1,262.20