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	$196.27	5.150%	$206.3779	$206.38	$206.40	$206.40
Purchase #2	$57.82	6.302%	$61.4638	$61.46	$61.45	$61.50
Purchase #3	$210.98	4.344%	$220.145	$220.15	$220.15	$220.10
Purchase #4	$247.83	3.193%	$255.7432	$255.74	$255.75	$255.70
Purchase #5	$88.64	6.518%	$94.4176	$94.42	$94.40	$94.40
Purchase #6	$140.38	7.539%	$150.9632	$150.96	$150.95	$151.00
Purchase #7	$123.88	3.704%	$128.4685	$128.47	$128.45	$128.50
7 purchase totals =	$1,065.80		$1,117.5792	$1,117.58	$1,117.55	$1,117.60