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	$71.37	6.704%	$76.1546	$76.15	$76.15	$76.20
Purchase #2	$37.62	9.325%	$41.1281	$41.13	$41.15	$41.10
Purchase #3	$148.43	7.343%	$159.3292	$159.33	$159.35	$159.30
Purchase #4	$144.87	9.818%	$159.0933	$159.09	$159.10	$159.10
Purchase #5	$174.82	8.745%	$190.108	$190.11	$190.10	$190.10
Purchase #6	$248.26	6.814%	$265.1764	$265.18	$265.20	$265.20
Purchase #7	$151.69	3.160%	$156.4834	$156.48	$156.50	$156.50
7 purchase totals =	$977.06		$1,047.4730	$1,047.47	$1,047.55	$1,047.50