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	$220.83	7.122%	$236.5575	$236.56	$236.55	$236.60
Purchase #2	$221.58	7.872%	$239.0228	$239.02	$239.00	$239.00
Purchase #3	$150.99	3.361%	$156.0648	$156.06	$156.05	$156.10
Purchase #4	$64.83	12.433%	$72.8903	$72.89	$72.90	$72.90
Purchase #5	$139.47	6.310%	$148.2706	$148.27	$148.25	$148.30
Purchase #6	$57.38	4.850%	$60.1629	$60.16	$60.15	$60.20
Purchase #7	$152.39	12.165%	$170.9282	$170.93	$170.95	$170.90
7 purchase totals =	$1,007.47		$1,083.8971	$1,083.89	$1,083.85	$1,084.00