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	$161.71	11.649%	$180.5476	$180.55	$180.55	$180.50
Purchase #2	$86.94	3.212%	$89.7325	$89.73	$89.75	$89.70
Purchase #3	$188.46	4.111%	$196.2076	$196.21	$196.20	$196.20
Purchase #4	$136.36	13.337%	$154.5463	$154.55	$154.55	$154.50
Purchase #5	$55.77	11.392%	$62.1233	$62.12	$62.10	$62.10
Purchase #6	$145.58	4.327%	$151.8792	$151.88	$151.90	$151.90
Purchase #7	$176.27	4.207%	$183.6857	$183.69	$183.70	$183.70
7 purchase totals =	$951.09		$1,018.7222	$1,018.73	$1,018.75	$1,018.60