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	$142.39	4.114%	$148.2479	$148.25	$148.25	$148.20
Purchase #2	$41.86	4.336%	$43.675	$43.68	$43.70	$43.70
Purchase #3	$82.76	5.584%	$87.3813	$87.38	$87.40	$87.40
Purchase #4	$197.97	4.486%	$206.8509	$206.85	$206.85	$206.90
Purchase #5	$55.95	6.295%	$59.4721	$59.47	$59.45	$59.50
Purchase #6	$104.87	3.612%	$108.6579	$108.66	$108.65	$108.70
Purchase #7	$167.50	5.258%	$176.3072	$176.31	$176.30	$176.30
7 purchase totals =	$793.30		$830.5923	$830.60	$830.60	$830.70