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	$115.89	10.334%	$127.8661	$127.87	$127.85	$127.90
Purchase #2	$80.54	8.318%	$87.2393	$87.24	$87.25	$87.20
Purchase #3	$43.65	7.268%	$46.8225	$46.82	$46.80	$46.80
Purchase #4	$36.68	10.597%	$40.567	$40.57	$40.55	$40.60
Purchase #5	$56.39	13.809%	$64.1769	$64.18	$64.20	$64.20
Purchase #6	$137.74	8.794%	$149.8529	$149.85	$149.85	$149.90
Purchase #7	$137.86	10.728%	$152.6496	$152.65	$152.65	$152.60
7 purchase totals =	$608.75		$669.1743	$669.18	$669.15	$669.20