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	$122.86	5.773%	$129.9527	$129.95	$129.95	$130.00
Purchase #2	$145.93	5.813%	$154.4129	$154.41	$154.40	$154.40
Purchase #3	$179.75	3.112%	$185.3438	$185.34	$185.35	$185.30
Purchase #4	$82.80	3.196%	$85.4463	$85.45	$85.45	$85.40
Purchase #5	$78.92	5.591%	$83.3324	$83.33	$83.35	$83.30
Purchase #6	$250.34	11.698%	$279.6248	$279.62	$279.60	$279.60
Purchase #7	$33.25	10.474%	$36.7326	$36.73	$36.75	$36.70
7 purchase totals =	$893.85		$954.8455	$954.83	$954.85	$954.70