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	$121.33	5.195%	$127.6331	$127.63	$127.65	$127.60
Purchase #2	$149.73	7.127%	$160.4013	$160.40	$160.40	$160.40
Purchase #3	$105.32	3.543%	$109.0515	$109.05	$109.05	$109.10
Purchase #4	$175.27	5.859%	$185.5391	$185.54	$185.55	$185.50
Purchase #5	$82.47	7.763%	$88.8721	$88.87	$88.85	$88.90
Purchase #6	$178.96	12.172%	$200.743	$200.74	$200.75	$200.70
Purchase #7	$158.62	7.327%	$170.2421	$170.24	$170.25	$170.20
7 purchase totals =	$971.70		$1,042.4822	$1,042.47	$1,042.50	$1,042.40