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	$172.71	5.314%	$181.8878	$181.89	$181.90	$181.90
Purchase #2	$68.29	10.133%	$75.2098	$75.21	$75.20	$75.20
Purchase #3	$205.96	8.343%	$223.1432	$223.14	$223.15	$223.10
Purchase #4	$74.77	5.254%	$78.6984	$78.70	$78.70	$78.70
Purchase #5	$219.69	6.173%	$233.2515	$233.25	$233.25	$233.30
Purchase #6	$89.90	5.713%	$95.036	$95.04	$95.05	$95.00
Purchase #7	$107.56	7.236%	$115.343	$115.34	$115.35	$115.30
7 purchase totals =	$938.88		$1,002.5697	$1,002.57	$1,002.60	$1,002.50