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	$177.25	3.606%	$183.6416	$183.64	$183.65	$183.60
Purchase #2	$179.88	7.146%	$192.7342	$192.73	$192.75	$192.70
Purchase #3	$185.96	13.835%	$211.6876	$211.69	$211.70	$211.70
Purchase #4	$74.72	7.155%	$80.0662	$80.07	$80.05	$80.10
Purchase #5	$141.55	12.110%	$158.6917	$158.69	$158.70	$158.70
Purchase #6	$45.93	6.406%	$48.8723	$48.87	$48.85	$48.90
Purchase #7	$122.89	3.615%	$127.3325	$127.33	$127.35	$127.30
7 purchase totals =	$928.18		$1,003.0261	$1,003.02	$1,003.05	$1,003.00