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	$248.31	6.359%	$264.1	$264.10	$264.10	$264.10
Purchase #2	$196.94	8.200%	$213.0891	$213.09	$213.10	$213.10
Purchase #3	$100.44	9.389%	$109.8703	$109.87	$109.85	$109.90
Purchase #4	$57.70	8.830%	$62.7949	$62.79	$62.80	$62.80
Purchase #5	$172.35	8.389%	$186.8084	$186.81	$186.80	$186.80
Purchase #6	$157.73	9.342%	$172.4651	$172.47	$172.45	$172.50
Purchase #7	$88.33	13.386%	$100.1539	$100.15	$100.15	$100.20
7 purchase totals =	$1,021.80		$1,109.2817	$1,109.28	$1,109.25	$1,109.40