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	$101.33	10.836%	$112.3101	$112.31	$112.30	$112.30
Purchase #2	$147.44	11.465%	$164.344	$164.34	$164.35	$164.30
Purchase #3	$162.51	13.538%	$184.5106	$184.51	$184.50	$184.50
Purchase #4	$134.25	7.491%	$144.3067	$144.31	$144.30	$144.30
Purchase #5	$232.75	11.144%	$258.6877	$258.69	$258.70	$258.70
Purchase #6	$203.64	3.108%	$209.9691	$209.97	$209.95	$210.00
Purchase #7	$118.86	5.401%	$125.2796	$125.28	$125.30	$125.30
7 purchase totals =	$1,100.78		$1,199.4078	$1,199.41	$1,199.40	$1,199.40