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	$236.85	4.156%	$246.6935	$246.69	$246.70	$246.70
Purchase #2	$240.89	9.769%	$264.4225	$264.42	$264.40	$264.40
Purchase #3	$232.77	9.537%	$254.9693	$254.97	$254.95	$255.00
Purchase #4	$225.70	7.485%	$242.5936	$242.59	$242.60	$242.60
Purchase #5	$12.27	10.429%	$13.5496	$13.55	$13.55	$13.50
Purchase #6	$179.71	3.199%	$185.4589	$185.46	$185.45	$185.50
Purchase #7	$59.32	4.602%	$62.0499	$62.05	$62.05	$62.00
7 purchase totals =	$1,187.51		$1,269.7373	$1,269.73	$1,269.70	$1,269.70