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	$150.82	12.398%	$169.5187	$169.52	$169.50	$169.50
Purchase #2	$75.61	4.194%	$78.7811	$78.78	$78.80	$78.80
Purchase #3	$161.55	4.747%	$169.2188	$169.22	$169.20	$169.20
Purchase #4	$205.94	6.599%	$219.53	$219.53	$219.55	$219.50
Purchase #5	$178.37	6.789%	$190.4795	$190.48	$190.50	$190.50
Purchase #6	$147.70	13.225%	$167.2333	$167.23	$167.25	$167.20
Purchase #7	$6.39	12.111%	$7.1639	$7.16	$7.15	$7.20
7 purchase totals =	$926.38		$1,001.9253	$1,001.92	$1,001.95	$1,001.90