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	$164.93	4.201%	$171.8587	$171.86	$171.85	$171.90
Purchase #2	$42.91	6.627%	$45.7536	$45.75	$45.75	$45.80
Purchase #3	$131.56	7.467%	$141.3836	$141.38	$141.40	$141.40
Purchase #4	$206.53	7.187%	$221.3733	$221.37	$221.35	$221.40
Purchase #5	$238.49	6.402%	$253.7581	$253.76	$253.75	$253.80
Purchase #6	$23.86	4.162%	$24.8531	$24.85	$24.85	$24.90
Purchase #7	$148.36	11.874%	$165.9763	$165.98	$166.00	$166.00
7 purchase totals =	$956.64		$1,024.9567	$1,024.95	$1,024.95	$1,025.20