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	$67.77	7.820%	$73.0696	$73.07	$73.05	$73.10
Purchase #2	$196.56	8.659%	$213.5801	$213.58	$213.60	$213.60
Purchase #3	$202.79	9.488%	$222.0307	$222.03	$222.05	$222.00
Purchase #4	$166.41	5.241%	$175.1315	$175.13	$175.15	$175.10
Purchase #5	$241.31	5.181%	$253.8123	$253.81	$253.80	$253.80
Purchase #6	$7.29	6.620%	$7.7726	$7.77	$7.75	$7.80
Purchase #7	$52.92	7.585%	$56.934	$56.93	$56.95	$56.90
7 purchase totals =	$935.05		$1,002.3308	$1,002.32	$1,002.35	$1,002.30