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	$139.82	11.155%	$155.4169	$155.42	$155.40	$155.40
Purchase #2	$46.92	4.511%	$49.0366	$49.04	$49.05	$49.00
Purchase #3	$222.67	9.421%	$243.6477	$243.65	$243.65	$243.60
Purchase #4	$223.72	13.374%	$253.6403	$253.64	$253.65	$253.60
Purchase #5	$55.76	6.443%	$59.3526	$59.35	$59.35	$59.40
Purchase #6	$154.63	13.435%	$175.4045	$175.40	$175.40	$175.40
Purchase #7	$219.52	11.611%	$245.0085	$245.01	$245.00	$245.00
7 purchase totals =	$1,063.04		$1,181.5071	$1,181.51	$1,181.50	$1,181.40