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	$169.64	8.736%	$184.4598	$184.46	$184.45	$184.50
Purchase #2	$73.50	11.830%	$82.1951	$82.20	$82.20	$82.20
Purchase #3	$117.63	10.222%	$129.6541	$129.65	$129.65	$129.70
Purchase #4	$134.79	12.471%	$151.5997	$151.60	$151.60	$151.60
Purchase #5	$70.92	10.239%	$78.1815	$78.18	$78.20	$78.20
Purchase #6	$225.64	12.794%	$254.5084	$254.51	$254.50	$254.50
Purchase #7	$212.74	5.224%	$223.8535	$223.85	$223.85	$223.90
7 purchase totals =	$1,004.86		$1,104.4521	$1,104.45	$1,104.45	$1,104.60