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	$176.99	6.161%	$187.8944	$187.89	$187.90	$187.90
Purchase #2	$68.28	11.521%	$76.1465	$76.15	$76.15	$76.10
Purchase #3	$129.50	8.603%	$140.6409	$140.64	$140.65	$140.60
Purchase #4	$91.91	3.432%	$95.0644	$95.06	$95.05	$95.10
Purchase #5	$52.39	13.165%	$59.2871	$59.29	$59.30	$59.30
Purchase #6	$222.63	11.462%	$248.1479	$248.15	$248.15	$248.10
Purchase #7	$238.92	4.554%	$249.8004	$249.80	$249.80	$249.80
7 purchase totals =	$980.62		$1,056.9816	$1,056.98	$1,057.00	$1,056.90