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	$184.61	7.529%	$198.5093	$198.51	$198.50	$198.50
Purchase #2	$171.57	8.154%	$185.5598	$185.56	$185.55	$185.60
Purchase #3	$152.36	12.803%	$171.8667	$171.87	$171.85	$171.90
Purchase #4	$50.31	12.713%	$56.7059	$56.71	$56.70	$56.70
Purchase #5	$163.92	4.265%	$170.9112	$170.91	$170.90	$170.90
Purchase #6	$169.61	6.631%	$180.8568	$180.86	$180.85	$180.90
Purchase #7	$89.28	11.303%	$99.3713	$99.37	$99.35	$99.40
7 purchase totals =	$981.66		$1,063.7810	$1,063.79	$1,063.70	$1,063.90