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	$163.27	10.449%	$180.3301	$180.33	$180.35	$180.30
Purchase #2	$157.70	11.207%	$175.3734	$175.37	$175.35	$175.40
Purchase #3	$161.26	13.378%	$182.8334	$182.83	$182.85	$182.80
Purchase #4	$99.65	11.448%	$111.0579	$111.06	$111.05	$111.10
Purchase #5	$37.38	12.695%	$42.1254	$42.13	$42.15	$42.10
Purchase #6	$31.29	5.291%	$32.9456	$32.95	$32.95	$32.90
Purchase #7	$127.49	11.742%	$142.4599	$142.46	$142.45	$142.50
7 purchase totals =	$778.04		$867.1257	$867.13	$867.15	$867.10