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	$173.71	11.296%	$193.3323	$193.33	$193.35	$193.30
Purchase #2	$197.74	7.258%	$212.092	$212.09	$212.10	$212.10
Purchase #3	$171.86	11.331%	$191.3335	$191.33	$191.35	$191.30
Purchase #4	$37.70	12.773%	$42.5154	$42.52	$42.50	$42.50
Purchase #5	$236.33	11.865%	$264.3706	$264.37	$264.35	$264.40
Purchase #6	$95.62	13.755%	$108.7725	$108.77	$108.75	$108.80
Purchase #7	$170.63	3.423%	$176.4707	$176.47	$176.45	$176.50
7 purchase totals =	$1,083.59		$1,188.8870	$1,188.88	$1,188.85	$1,188.90