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	$144.89	7.777%	$156.1581	$156.16	$156.15	$156.20
Purchase #2	$154.96	4.784%	$162.3733	$162.37	$162.35	$162.40
Purchase #3	$201.46	8.735%	$219.0575	$219.06	$219.05	$219.10
Purchase #4	$59.91	9.589%	$65.6548	$65.65	$65.65	$65.70
Purchase #5	$37.51	7.102%	$40.174	$40.17	$40.15	$40.20
Purchase #6	$224.98	13.832%	$256.0992	$256.10	$256.10	$256.10
Purchase #7	$230.84	5.290%	$243.0514	$243.05	$243.05	$243.10
7 purchase totals =	$1,054.55		$1,142.5683	$1,142.56	$1,142.50	$1,142.80