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	$142.28	9.458%	$155.7368	$155.74	$155.75	$155.70
Purchase #2	$46.38	6.530%	$49.4086	$49.41	$49.40	$49.40
Purchase #3	$194.50	9.728%	$213.421	$213.42	$213.40	$213.40
Purchase #4	$182.34	4.603%	$190.7331	$190.73	$190.75	$190.70
Purchase #5	$130.26	12.550%	$146.6076	$146.61	$146.60	$146.60
Purchase #6	$82.72	8.681%	$89.9009	$89.90	$89.90	$89.90
Purchase #7	$237.35	7.249%	$254.5555	$254.56	$254.55	$254.60
7 purchase totals =	$1,015.83		$1,100.3635	$1,100.37	$1,100.35	$1,100.30