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	$55.75	10.471%	$61.5876	$61.59	$61.60	$61.60
Purchase #2	$56.28	5.793%	$59.5403	$59.54	$59.55	$59.50
Purchase #3	$210.46	12.506%	$236.7801	$236.78	$236.80	$236.80
Purchase #4	$83.45	4.864%	$87.509	$87.51	$87.50	$87.50
Purchase #5	$204.32	10.204%	$225.1688	$225.17	$225.15	$225.20
Purchase #6	$250.53	7.794%	$270.0563	$270.06	$270.05	$270.10
Purchase #7	$159.89	8.296%	$173.1545	$173.15	$173.15	$173.20
7 purchase totals =	$1,020.68		$1,113.7966	$1,113.80	$1,113.80	$1,113.90