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	$158.72	7.397%	$170.4605	$170.46	$170.45	$170.50
Purchase #2	$76.95	6.747%	$82.1418	$82.14	$82.15	$82.10
Purchase #3	$189.80	3.609%	$196.6499	$196.65	$196.65	$196.60
Purchase #4	$144.84	7.712%	$156.0101	$156.01	$156.00	$156.00
Purchase #5	$235.91	9.759%	$258.9325	$258.93	$258.95	$258.90
Purchase #6	$194.64	5.601%	$205.5418	$205.54	$205.55	$205.50
Purchase #7	$96.61	7.811%	$104.1562	$104.16	$104.15	$104.20
7 purchase totals =	$1,097.47		$1,173.8928	$1,173.89	$1,173.90	$1,173.80