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	$243.37	5.526%	$256.8186	$256.82	$256.80	$256.80
Purchase #2	$58.36	10.444%	$64.4551	$64.46	$64.45	$64.50
Purchase #3	$158.35	7.650%	$170.4638	$170.46	$170.45	$170.50
Purchase #4	$139.35	10.736%	$154.3106	$154.31	$154.30	$154.30
Purchase #5	$147.25	13.329%	$166.877	$166.88	$166.90	$166.90
Purchase #6	$116.65	11.682%	$130.2771	$130.28	$130.30	$130.30
Purchase #7	$184.27	11.455%	$205.3781	$205.38	$205.40	$205.40
7 purchase totals =	$1,047.60		$1,148.5803	$1,148.59	$1,148.60	$1,148.70