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	$143.67	11.874%	$160.7294	$160.73	$160.75	$160.70
Purchase #2	$233.74	7.763%	$251.8852	$251.89	$251.90	$251.90
Purchase #3	$72.89	12.510%	$82.0085	$82.01	$82.00	$82.00
Purchase #4	$54.82	13.687%	$62.3232	$62.32	$62.30	$62.30
Purchase #5	$196.87	13.496%	$223.4396	$223.44	$223.45	$223.40
Purchase #6	$86.71	8.448%	$94.0353	$94.04	$94.05	$94.00
Purchase #7	$195.46	13.123%	$221.1102	$221.11	$221.10	$221.10
7 purchase totals =	$984.16		$1,095.5314	$1,095.54	$1,095.55	$1,095.40