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	$141.82	6.698%	$151.3191	$151.32	$151.30	$151.30
Purchase #2	$242.33	3.306%	$250.3414	$250.34	$250.35	$250.30
Purchase #3	$47.50	13.579%	$53.95	$53.95	$53.95	$54.00
Purchase #4	$40.72	7.617%	$43.8216	$43.82	$43.80	$43.80
Purchase #5	$59.26	5.551%	$62.5495	$62.55	$62.55	$62.50
Purchase #6	$187.38	9.765%	$205.6777	$205.68	$205.70	$205.70
Purchase #7	$219.27	12.649%	$247.0055	$247.01	$247.00	$247.00
7 purchase totals =	$938.28		$1,014.6648	$1,014.67	$1,014.65	$1,014.60