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	$170.89	8.618%	$185.6173	$185.62	$185.60	$185.60
Purchase #2	$178.58	3.499%	$184.8285	$184.83	$184.85	$184.80
Purchase #3	$37.43	7.657%	$40.296	$40.30	$40.30	$40.30
Purchase #4	$166.56	12.393%	$187.2018	$187.20	$187.20	$187.20
Purchase #5	$75.34	8.394%	$81.664	$81.66	$81.65	$81.70
Purchase #6	$174.33	6.415%	$185.5133	$185.51	$185.50	$185.50
Purchase #7	$234.37	5.113%	$246.3533	$246.35	$246.35	$246.40
7 purchase totals =	$1,037.50		$1,111.4742	$1,111.47	$1,111.45	$1,111.50