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	$197.72	3.185%	$204.0174	$204.02	$204.00	$204.00
Purchase #2	$94.45	4.140%	$98.3602	$98.36	$98.35	$98.40
Purchase #3	$35.31	11.576%	$39.3975	$39.40	$39.40	$39.40
Purchase #4	$250.74	11.198%	$278.8179	$278.82	$278.80	$278.80
Purchase #5	$249.30	12.474%	$280.3977	$280.40	$280.40	$280.40
Purchase #6	$172.89	10.705%	$191.3979	$191.40	$191.40	$191.40
Purchase #7	$186.97	11.322%	$208.1387	$208.14	$208.15	$208.10
7 purchase totals =	$1,187.38		$1,300.5273	$1,300.54	$1,300.50	$1,300.50