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	$163.73	10.725%	$181.29	$181.29	$181.30	$181.30
Purchase #2	$100.63	11.550%	$112.2528	$112.25	$112.25	$112.30
Purchase #3	$52.32	4.734%	$54.7968	$54.80	$54.80	$54.80
Purchase #4	$140.77	8.765%	$153.1085	$153.11	$153.10	$153.10
Purchase #5	$111.31	5.596%	$117.5389	$117.54	$117.55	$117.50
Purchase #6	$53.27	10.795%	$59.0205	$59.02	$59.00	$59.00
Purchase #7	$240.32	8.649%	$261.1053	$261.11	$261.10	$261.10
7 purchase totals =	$862.35		$939.1128	$939.12	$939.10	$939.10