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	$208.35	5.506%	$219.8218	$219.82	$219.80	$219.80
Purchase #2	$31.32	6.501%	$33.3561	$33.36	$33.35	$33.40
Purchase #3	$238.46	4.710%	$249.6915	$249.69	$249.70	$249.70
Purchase #4	$237.50	7.558%	$255.4503	$255.45	$255.45	$255.50
Purchase #5	$228.92	6.616%	$244.0653	$244.07	$244.05	$244.10
Purchase #6	$162.47	6.417%	$172.8957	$172.90	$172.90	$172.90
Purchase #7	$40.73	13.111%	$46.0701	$46.07	$46.05	$46.10
7 purchase totals =	$1,147.75		$1,221.3508	$1,221.36	$1,221.30	$1,221.50