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	$146.32	10.811%	$162.1387	$162.14	$162.15	$162.10
Purchase #2	$227.72	13.349%	$258.1183	$258.12	$258.10	$258.10
Purchase #3	$41.57	9.282%	$45.4285	$45.43	$45.45	$45.40
Purchase #4	$238.29	13.485%	$270.4234	$270.42	$270.40	$270.40
Purchase #5	$55.37	7.367%	$59.4491	$59.45	$59.45	$59.40
Purchase #6	$234.49	4.158%	$244.2401	$244.24	$244.25	$244.20
Purchase #7	$98.96	9.272%	$108.1356	$108.14	$108.15	$108.10
7 purchase totals =	$1,042.72		$1,147.9337	$1,147.94	$1,147.95	$1,147.70