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	$184.47	3.691%	$191.2788	$191.28	$191.30	$191.30
Purchase #2	$77.79	11.691%	$86.8844	$86.88	$86.90	$86.90
Purchase #3	$53.54	4.783%	$56.1008	$56.10	$56.10	$56.10
Purchase #4	$130.29	12.430%	$146.485	$146.49	$146.50	$146.50
Purchase #5	$201.82	4.186%	$210.2682	$210.27	$210.25	$210.30
Purchase #6	$185.44	6.120%	$196.7889	$196.79	$196.80	$196.80
Purchase #7	$245.70	8.119%	$265.6484	$265.65	$265.65	$265.60
7 purchase totals =	$1,079.05		$1,153.4545	$1,153.46	$1,153.50	$1,153.50