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	$211.74	4.404%	$221.065	$221.07	$221.05	$221.10
Purchase #2	$241.64	9.347%	$264.2261	$264.23	$264.25	$264.20
Purchase #3	$12.38	5.743%	$13.091	$13.09	$13.10	$13.10
Purchase #4	$29.95	13.342%	$33.9459	$33.95	$33.95	$33.90
Purchase #5	$57.56	9.145%	$62.8239	$62.82	$62.80	$62.80
Purchase #6	$135.88	5.184%	$142.924	$142.92	$142.90	$142.90
Purchase #7	$171.93	11.116%	$191.0417	$191.04	$191.05	$191.00
7 purchase totals =	$861.08		$929.1176	$929.12	$929.10	$929.00