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	$165.25	8.595%	$179.4532	$179.45	$179.45	$179.50
Purchase #2	$84.50	10.384%	$93.2745	$93.27	$93.25	$93.30
Purchase #3	$173.37	6.642%	$184.8852	$184.89	$184.90	$184.90
Purchase #4	$99.58	6.578%	$106.1304	$106.13	$106.15	$106.10
Purchase #5	$157.30	6.258%	$167.1438	$167.14	$167.15	$167.10
Purchase #6	$180.97	3.839%	$187.9174	$187.92	$187.90	$187.90
Purchase #7	$137.43	3.165%	$141.7797	$141.78	$141.80	$141.80
7 purchase totals =	$998.40		$1,060.5842	$1,060.58	$1,060.60	$1,060.60