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	$112.33	12.112%	$125.9354	$125.94	$125.95	$125.90
Purchase #2	$69.72	3.300%	$72.0208	$72.02	$72.00	$72.00
Purchase #3	$50.89	11.260%	$56.6202	$56.62	$56.60	$56.60
Purchase #4	$192.75	13.673%	$219.1047	$219.10	$219.10	$219.10
Purchase #5	$24.94	12.652%	$28.0954	$28.10	$28.10	$28.10
Purchase #6	$49.56	9.201%	$54.12	$54.12	$54.10	$54.10
Purchase #7	$136.48	5.164%	$143.5278	$143.53	$143.55	$143.50
7 purchase totals =	$636.67		$699.4243	$699.43	$699.40	$699.30