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	$190.68	5.374%	$200.9271	$200.93	$200.95	$200.90
Purchase #2	$205.36	9.824%	$225.5346	$225.53	$225.55	$225.50
Purchase #3	$148.74	10.428%	$164.2506	$164.25	$164.25	$164.30
Purchase #4	$99.30	10.849%	$110.0731	$110.07	$110.05	$110.10
Purchase #5	$149.83	6.498%	$159.566	$159.57	$159.55	$159.60
Purchase #6	$50.56	6.465%	$53.8287	$53.83	$53.85	$53.80
Purchase #7	$75.35	11.387%	$83.9301	$83.93	$83.95	$83.90
7 purchase totals =	$919.82		$998.1102	$998.11	$998.15	$998.10