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	$39.62	9.549%	$43.4033	$43.40	$43.40	$43.40
Purchase #2	$196.40	4.308%	$204.8609	$204.86	$204.85	$204.90
Purchase #3	$94.73	4.667%	$99.151	$99.15	$99.15	$99.20
Purchase #4	$71.25	10.367%	$78.6365	$78.64	$78.65	$78.60
Purchase #5	$201.51	4.431%	$210.4389	$210.44	$210.45	$210.40
Purchase #6	$46.70	8.139%	$50.5009	$50.50	$50.50	$50.50
Purchase #7	$189.43	12.675%	$213.4403	$213.44	$213.45	$213.40
7 purchase totals =	$839.64		$900.4318	$900.43	$900.45	$900.40