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	$67.98	13.664%	$77.2688	$77.27	$77.25	$77.30
Purchase #2	$35.40	13.867%	$40.3089	$40.31	$40.30	$40.30
Purchase #3	$69.25	3.854%	$71.9189	$71.92	$71.90	$71.90
Purchase #4	$109.47	13.751%	$124.5232	$124.52	$124.50	$124.50
Purchase #5	$61.96	5.112%	$65.1274	$65.13	$65.15	$65.10
Purchase #6	$104.33	6.615%	$111.2314	$111.23	$111.25	$111.20
Purchase #7	$207.85	11.642%	$232.0479	$232.05	$232.05	$232.00
7 purchase totals =	$656.24		$722.4265	$722.43	$722.40	$722.30