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	$114.32	4.364%	$119.3089	$119.31	$119.30	$119.30
Purchase #2	$176.53	11.485%	$196.8045	$196.80	$196.80	$196.80
Purchase #3	$40.29	10.607%	$44.5636	$44.56	$44.55	$44.60
Purchase #4	$49.48	6.424%	$52.6586	$52.66	$52.65	$52.70
Purchase #5	$67.51	10.613%	$74.6748	$74.67	$74.65	$74.70
Purchase #6	$250.47	9.407%	$274.0317	$274.03	$274.05	$274.00
Purchase #7	$213.46	12.851%	$240.8917	$240.89	$240.90	$240.90
7 purchase totals =	$912.06		$1,002.9338	$1,002.92	$1,002.90	$1,003.00