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	$125.63	12.722%	$141.6126	$141.61	$141.60	$141.60
Purchase #2	$78.53	4.468%	$82.0387	$82.04	$82.05	$82.00
Purchase #3	$104.95	5.245%	$110.4546	$110.45	$110.45	$110.50
Purchase #4	$34.27	8.155%	$37.0647	$37.06	$37.05	$37.10
Purchase #5	$65.28	7.706%	$70.3105	$70.31	$70.30	$70.30
Purchase #6	$147.87	11.662%	$165.1146	$165.11	$165.10	$165.10
Purchase #7	$131.35	8.777%	$142.8786	$142.88	$142.90	$142.90
7 purchase totals =	$687.88		$749.4743	$749.46	$749.45	$749.50