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	$47.45	11.783%	$53.041	$53.04	$53.05	$53.00
Purchase #2	$244.70	3.731%	$253.8298	$253.83	$253.85	$253.80
Purchase #3	$32.87	7.262%	$35.257	$35.26	$35.25	$35.30
Purchase #4	$153.82	13.363%	$174.375	$174.38	$174.40	$174.40
Purchase #5	$43.32	3.145%	$44.6824	$44.68	$44.70	$44.70
Purchase #6	$139.82	9.166%	$152.6359	$152.64	$152.65	$152.60
Purchase #7	$43.89	7.402%	$47.1387	$47.14	$47.15	$47.10
7 purchase totals =	$705.87		$760.9598	$760.97	$761.05	$760.90