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	$187.42	9.487%	$205.2005	$205.20	$205.20	$205.20
Purchase #2	$220.28	3.761%	$228.5647	$228.56	$228.55	$228.60
Purchase #3	$77.45	4.395%	$80.8539	$80.85	$80.85	$80.90
Purchase #4	$94.96	4.727%	$99.4488	$99.45	$99.45	$99.40
Purchase #5	$165.92	4.326%	$173.0977	$173.10	$173.10	$173.10
Purchase #6	$80.28	4.360%	$83.7802	$83.78	$83.80	$83.80
Purchase #7	$98.34	10.311%	$108.4798	$108.48	$108.50	$108.50
7 purchase totals =	$924.65		$979.4256	$979.42	$979.45	$979.50