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	$172.37	5.211%	$181.3522	$181.35	$181.35	$181.40
Purchase #2	$79.63	12.834%	$89.8497	$89.85	$89.85	$89.80
Purchase #3	$69.64	3.781%	$72.2731	$72.27	$72.25	$72.30
Purchase #4	$167.63	12.328%	$188.2954	$188.30	$188.30	$188.30
Purchase #5	$212.91	8.840%	$231.7312	$231.73	$231.75	$231.70
Purchase #6	$9.31	9.377%	$10.183	$10.18	$10.20	$10.20
Purchase #7	$55.27	8.425%	$59.9265	$59.93	$59.95	$59.90
7 purchase totals =	$766.76		$833.6111	$833.61	$833.65	$833.60