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	$223.95	4.515%	$234.0613	$234.06	$234.05	$234.10
Purchase #2	$73.91	6.472%	$78.6935	$78.69	$78.70	$78.70
Purchase #3	$100.28	4.773%	$105.0664	$105.07	$105.05	$105.10
Purchase #4	$115.58	7.505%	$124.2543	$124.25	$124.25	$124.30
Purchase #5	$113.33	6.366%	$120.5446	$120.54	$120.55	$120.50
Purchase #6	$238.82	11.407%	$266.0622	$266.06	$266.05	$266.10
Purchase #7	$13.67	13.153%	$15.468	$15.47	$15.45	$15.50
7 purchase totals =	$879.54		$944.1503	$944.14	$944.10	$944.30