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	$229.83	3.256%	$237.3133	$237.31	$237.30	$237.30
Purchase #2	$172.37	7.524%	$185.3391	$185.34	$185.35	$185.30
Purchase #3	$69.52	6.195%	$73.8268	$73.83	$73.85	$73.80
Purchase #4	$29.98	4.562%	$31.3477	$31.35	$31.35	$31.30
Purchase #5	$50.86	7.469%	$54.6587	$54.66	$54.65	$54.70
Purchase #6	$215.33	11.845%	$240.8358	$240.84	$240.85	$240.80
Purchase #7	$100.68	3.740%	$104.4454	$104.45	$104.45	$104.40
7 purchase totals =	$868.57		$927.7668	$927.78	$927.80	$927.60