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	$153.88	13.307%	$174.3568	$174.36	$174.35	$174.40
Purchase #2	$53.43	4.306%	$55.7307	$55.73	$55.75	$55.70
Purchase #3	$137.31	10.377%	$151.5587	$151.56	$151.55	$151.60
Purchase #4	$40.36	4.865%	$42.3235	$42.32	$42.30	$42.30
Purchase #5	$146.33	11.784%	$163.5735	$163.57	$163.55	$163.60
Purchase #6	$99.28	10.165%	$109.3718	$109.37	$109.35	$109.40
Purchase #7	$164.34	5.350%	$173.1322	$173.13	$173.15	$173.10
7 purchase totals =	$794.93		$870.0472	$870.04	$870.00	$870.10