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	$189.72	8.783%	$206.3831	$206.38	$206.40	$206.40
Purchase #2	$79.89	11.592%	$89.1508	$89.15	$89.15	$89.20
Purchase #3	$57.96	12.355%	$65.121	$65.12	$65.10	$65.10
Purchase #4	$211.81	10.447%	$233.9378	$233.94	$233.95	$233.90
Purchase #5	$143.91	3.204%	$148.5209	$148.52	$148.50	$148.50
Purchase #6	$98.68	10.586%	$109.1263	$109.13	$109.15	$109.10
Purchase #7	$174.85	3.417%	$180.8246	$180.82	$180.80	$180.80
7 purchase totals =	$956.82		$1,033.0645	$1,033.06	$1,033.05	$1,033.00