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	$237.50	5.860%	$251.4175	$251.42	$251.40	$251.40
Purchase #2	$165.85	4.558%	$173.4094	$173.41	$173.40	$173.40
Purchase #3	$143.48	12.320%	$161.1567	$161.16	$161.15	$161.20
Purchase #4	$70.85	12.805%	$79.9223	$79.92	$79.90	$79.90
Purchase #5	$194.79	9.494%	$213.2834	$213.28	$213.30	$213.30
Purchase #6	$18.79	7.607%	$20.2194	$20.22	$20.20	$20.20
Purchase #7	$99.47	12.206%	$111.6113	$111.61	$111.60	$111.60
7 purchase totals =	$930.73		$1,011.0200	$1,011.02	$1,010.95	$1,011.00