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	$72.55	5.456%	$76.5083	$76.51	$76.50	$76.50
Purchase #2	$90.61	8.144%	$97.9893	$97.99	$98.00	$98.00
Purchase #3	$182.69	7.367%	$196.1488	$196.15	$196.15	$196.10
Purchase #4	$94.63	9.800%	$103.9037	$103.90	$103.90	$103.90
Purchase #5	$206.76	13.222%	$234.0978	$234.10	$234.10	$234.10
Purchase #6	$180.25	10.623%	$199.398	$199.40	$199.40	$199.40
Purchase #7	$215.52	13.245%	$244.0656	$244.07	$244.05	$244.10
7 purchase totals =	$1,043.01		$1,152.1115	$1,152.12	$1,152.10	$1,152.10