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	$114.36	10.420%	$126.2763	$126.28	$126.30	$126.30
Purchase #2	$61.88	8.214%	$66.9628	$66.96	$66.95	$67.00
Purchase #3	$214.59	4.291%	$223.7981	$223.80	$223.80	$223.80
Purchase #4	$156.30	11.394%	$174.1088	$174.11	$174.10	$174.10
Purchase #5	$154.46	10.751%	$171.066	$171.07	$171.05	$171.10
Purchase #6	$192.31	4.361%	$200.6966	$200.70	$200.70	$200.70
Purchase #7	$152.55	7.603%	$164.1484	$164.15	$164.15	$164.10
7 purchase totals =	$1,046.45		$1,127.0570	$1,127.07	$1,127.05	$1,127.10