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	$138.73	9.160%	$151.4377	$151.44	$151.45	$151.40
Purchase #2	$208.72	7.233%	$223.8167	$223.82	$223.80	$223.80
Purchase #3	$173.67	9.265%	$189.7605	$189.76	$189.75	$189.80
Purchase #4	$181.75	6.332%	$193.2584	$193.26	$193.25	$193.30
Purchase #5	$59.96	4.313%	$62.5461	$62.55	$62.55	$62.50
Purchase #6	$152.69	7.814%	$164.6212	$164.62	$164.60	$164.60
Purchase #7	$73.80	7.743%	$79.5143	$79.51	$79.50	$79.50
7 purchase totals =	$989.32		$1,064.9549	$1,064.96	$1,064.90	$1,064.90