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	$229.56	6.170%	$243.7239	$243.72	$243.70	$243.70
Purchase #2	$103.50	7.757%	$111.5285	$111.53	$111.55	$111.50
Purchase #3	$201.54	12.722%	$227.1799	$227.18	$227.20	$227.20
Purchase #4	$68.91	7.156%	$73.8412	$73.84	$73.85	$73.80
Purchase #5	$122.99	11.856%	$137.5717	$137.57	$137.55	$137.60
Purchase #6	$183.28	4.363%	$191.2765	$191.28	$191.30	$191.30
Purchase #7	$36.51	10.524%	$40.3523	$40.35	$40.35	$40.40
7 purchase totals =	$946.29		$1,025.4740	$1,025.47	$1,025.50	$1,025.50