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	$196.61	7.122%	$210.6126	$210.61	$210.60	$210.60
Purchase #2	$78.88	3.298%	$81.4815	$81.48	$81.50	$81.50
Purchase #3	$64.83	12.848%	$73.1594	$73.16	$73.15	$73.20
Purchase #4	$142.54	11.181%	$158.4774	$158.48	$158.50	$158.50
Purchase #5	$67.61	11.111%	$75.1221	$75.12	$75.10	$75.10
Purchase #6	$166.87	3.282%	$172.3467	$172.35	$172.35	$172.30
Purchase #7	$243.46	6.686%	$259.7377	$259.74	$259.75	$259.70
7 purchase totals =	$960.80		$1,030.9374	$1,030.94	$1,030.95	$1,030.90