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	$135.96	12.413%	$152.8367	$152.84	$152.85	$152.80
Purchase #2	$168.44	7.815%	$181.6036	$181.60	$181.60	$181.60
Purchase #3	$117.58	10.785%	$130.261	$130.26	$130.25	$130.30
Purchase #4	$198.87	12.533%	$223.7944	$223.79	$223.80	$223.80
Purchase #5	$53.38	10.827%	$59.1595	$59.16	$59.15	$59.20
Purchase #6	$62.75	13.396%	$71.156	$71.16	$71.15	$71.20
Purchase #7	$72.90	8.339%	$78.9791	$78.98	$79.00	$79.00
7 purchase totals =	$809.88		$897.7903	$897.79	$897.80	$897.90