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	$239.27	8.507%	$259.6247	$259.62	$259.60	$259.60
Purchase #2	$141.95	6.642%	$151.3783	$151.38	$151.40	$151.40
Purchase #3	$157.51	6.147%	$167.1921	$167.19	$167.20	$167.20
Purchase #4	$144.65	12.425%	$162.6228	$162.62	$162.60	$162.60
Purchase #5	$28.52	13.776%	$32.4489	$32.45	$32.45	$32.40
Purchase #6	$19.46	9.739%	$21.3552	$21.36	$21.35	$21.40
Purchase #7	$238.37	11.226%	$265.1294	$265.13	$265.15	$265.10
7 purchase totals =	$969.73		$1,059.7514	$1,059.75	$1,059.75	$1,059.70