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	$185.62	5.723%	$196.243	$196.24	$196.25	$196.20
Purchase #2	$163.29	6.580%	$174.0345	$174.03	$174.05	$174.00
Purchase #3	$80.39	3.623%	$83.3025	$83.30	$83.30	$83.30
Purchase #4	$199.25	10.271%	$219.715	$219.72	$219.70	$219.70
Purchase #5	$133.43	10.403%	$147.3107	$147.31	$147.30	$147.30
Purchase #6	$46.86	12.530%	$52.7316	$52.73	$52.75	$52.70
Purchase #7	$95.56	8.277%	$103.4695	$103.47	$103.45	$103.50
7 purchase totals =	$904.40		$976.8068	$976.80	$976.80	$976.70