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	$219.32	10.419%	$242.171	$242.17	$242.15	$242.20
Purchase #2	$13.90	3.821%	$14.4311	$14.43	$14.45	$14.40
Purchase #3	$26.26	4.501%	$27.442	$27.44	$27.45	$27.40
Purchase #4	$203.67	10.141%	$224.3242	$224.32	$224.30	$224.30
Purchase #5	$84.45	5.518%	$89.11	$89.11	$89.10	$89.10
Purchase #6	$74.34	10.476%	$82.1279	$82.13	$82.15	$82.10
Purchase #7	$51.40	4.769%	$53.8513	$53.85	$53.85	$53.90
7 purchase totals =	$673.34		$733.4575	$733.45	$733.45	$733.40