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	$93.33	6.567%	$99.459	$99.46	$99.45	$99.50
Purchase #2	$28.64	10.199%	$31.561	$31.56	$31.55	$31.60
Purchase #3	$191.73	11.416%	$213.6179	$213.62	$213.60	$213.60
Purchase #4	$184.84	9.468%	$202.3407	$202.34	$202.35	$202.30
Purchase #5	$146.44	4.162%	$152.5348	$152.53	$152.55	$152.50
Purchase #6	$172.27	10.744%	$190.7787	$190.78	$190.80	$190.80
Purchase #7	$128.74	9.137%	$140.503	$140.50	$140.50	$140.50
7 purchase totals =	$945.99		$1,030.7951	$1,030.79	$1,030.80	$1,030.80