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	$174.59	8.419%	$189.2887	$189.29	$189.30	$189.30
Purchase #2	$245.26	12.493%	$275.9003	$275.90	$275.90	$275.90
Purchase #3	$16.61	10.715%	$18.3898	$18.39	$18.40	$18.40
Purchase #4	$147.45	5.788%	$155.9844	$155.98	$156.00	$156.00
Purchase #5	$229.86	12.793%	$259.266	$259.27	$259.25	$259.30
Purchase #6	$238.60	3.656%	$247.3232	$247.32	$247.30	$247.30
Purchase #7	$211.94	12.395%	$238.21	$238.21	$238.20	$238.20
7 purchase totals =	$1,264.31		$1,384.3624	$1,384.36	$1,384.35	$1,384.40