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	$111.40	7.340%	$119.5768	$119.58	$119.60	$119.60
Purchase #2	$145.66	12.814%	$164.3249	$164.32	$164.30	$164.30
Purchase #3	$229.96	7.745%	$247.7704	$247.77	$247.75	$247.80
Purchase #4	$155.50	7.842%	$167.6943	$167.69	$167.70	$167.70
Purchase #5	$91.41	10.330%	$100.8527	$100.85	$100.85	$100.90
Purchase #6	$184.29	9.417%	$201.6446	$201.64	$201.65	$201.60
Purchase #7	$157.75	4.323%	$164.5695	$164.57	$164.55	$164.60
7 purchase totals =	$1,075.97		$1,166.4332	$1,166.42	$1,166.40	$1,166.50