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	$153.67	3.747%	$159.428	$159.43	$159.45	$159.40
Purchase #2	$86.30	9.298%	$94.3242	$94.32	$94.30	$94.30
Purchase #3	$43.56	11.163%	$48.4226	$48.42	$48.40	$48.40
Purchase #4	$219.44	11.426%	$244.5132	$244.51	$244.50	$244.50
Purchase #5	$185.65	3.557%	$192.2536	$192.25	$192.25	$192.30
Purchase #6	$156.93	7.399%	$168.5413	$168.54	$168.55	$168.50
Purchase #7	$61.75	9.273%	$67.4761	$67.48	$67.50	$67.50
7 purchase totals =	$907.30		$974.9590	$974.95	$974.95	$974.90