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	$96.59	3.220%	$99.7002	$99.70	$99.70	$99.70
Purchase #2	$248.57	6.550%	$264.8513	$264.85	$264.85	$264.90
Purchase #3	$67.69	5.373%	$71.327	$71.33	$71.35	$71.30
Purchase #4	$222.47	12.430%	$250.123	$250.12	$250.10	$250.10
Purchase #5	$226.50	11.755%	$253.1251	$253.13	$253.15	$253.10
Purchase #6	$223.98	6.314%	$238.1221	$238.12	$238.10	$238.10
Purchase #7	$19.94	5.578%	$21.0523	$21.05	$21.05	$21.10
7 purchase totals =	$1,105.74		$1,198.3010	$1,198.30	$1,198.30	$1,198.30