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	$250.72	7.339%	$269.1203	$269.12	$269.10	$269.10
Purchase #2	$226.92	10.285%	$250.2587	$250.26	$250.25	$250.30
Purchase #3	$73.34	5.161%	$77.1251	$77.13	$77.15	$77.10
Purchase #4	$179.28	3.643%	$185.8112	$185.81	$185.80	$185.80
Purchase #5	$248.62	5.530%	$262.3687	$262.37	$262.35	$262.40
Purchase #6	$92.72	4.185%	$96.6003	$96.60	$96.60	$96.60
Purchase #7	$69.90	12.568%	$78.685	$78.69	$78.70	$78.70
7 purchase totals =	$1,141.50		$1,219.9693	$1,219.98	$1,219.95	$1,220.00