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	$64.83	11.396%	$72.218	$72.22	$72.20	$72.20
Purchase #2	$110.26	5.834%	$116.6926	$116.69	$116.70	$116.70
Purchase #3	$79.83	8.712%	$86.7848	$86.78	$86.80	$86.80
Purchase #4	$142.70	6.387%	$151.8142	$151.81	$151.80	$151.80
Purchase #5	$184.92	12.732%	$208.464	$208.46	$208.45	$208.50
Purchase #6	$222.31	12.764%	$250.6856	$250.69	$250.70	$250.70
Purchase #7	$18.32	7.699%	$19.7305	$19.73	$19.75	$19.70
7 purchase totals =	$823.17		$906.3897	$906.38	$906.40	$906.40