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	$138.85	11.457%	$154.758	$154.76	$154.75	$154.80
Purchase #2	$110.89	3.397%	$114.6569	$114.66	$114.65	$114.70
Purchase #3	$214.54	9.316%	$234.5265	$234.53	$234.55	$234.50
Purchase #4	$167.60	12.860%	$189.1534	$189.15	$189.15	$189.20
Purchase #5	$89.45	7.761%	$96.3922	$96.39	$96.40	$96.40
Purchase #6	$152.26	9.498%	$166.7217	$166.72	$166.70	$166.70
Purchase #7	$57.93	13.753%	$65.8971	$65.90	$65.90	$65.90
7 purchase totals =	$931.52		$1,022.1058	$1,022.11	$1,022.10	$1,022.20