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	$125.39	3.779%	$130.1285	$130.13	$130.15	$130.10
Purchase #2	$96.35	5.760%	$101.8998	$101.90	$101.90	$101.90
Purchase #3	$144.28	12.870%	$162.8488	$162.85	$162.85	$162.80
Purchase #4	$198.91	12.296%	$223.368	$223.37	$223.35	$223.40
Purchase #5	$189.30	11.277%	$210.6474	$210.65	$210.65	$210.60
Purchase #6	$155.34	7.172%	$166.481	$166.48	$166.50	$166.50
Purchase #7	$103.47	12.145%	$116.0364	$116.04	$116.05	$116.00
7 purchase totals =	$1,013.04		$1,111.4099	$1,111.42	$1,111.45	$1,111.30