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	$209.86	5.649%	$221.715	$221.72	$221.70	$221.70
Purchase #2	$245.56	6.660%	$261.9143	$261.91	$261.90	$261.90
Purchase #3	$116.77	9.507%	$127.8713	$127.87	$127.85	$127.90
Purchase #4	$231.76	5.810%	$245.2253	$245.23	$245.25	$245.20
Purchase #5	$198.91	8.784%	$216.3823	$216.38	$216.40	$216.40
Purchase #6	$195.95	8.798%	$213.1897	$213.19	$213.20	$213.20
Purchase #7	$59.97	12.219%	$67.2977	$67.30	$67.30	$67.30
7 purchase totals =	$1,258.78		$1,353.5956	$1,353.60	$1,353.60	$1,353.60