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	$224.71	5.120%	$236.2152	$236.22	$236.20	$236.20
Purchase #2	$154.79	10.693%	$171.3417	$171.34	$171.35	$171.30
Purchase #3	$87.76	13.594%	$99.6901	$99.69	$99.70	$99.70
Purchase #4	$132.95	9.384%	$145.426	$145.43	$145.45	$145.40
Purchase #5	$62.74	4.696%	$65.6863	$65.69	$65.70	$65.70
Purchase #6	$188.57	11.540%	$210.331	$210.33	$210.35	$210.30
Purchase #7	$41.38	5.221%	$43.5404	$43.54	$43.55	$43.50
7 purchase totals =	$892.90		$972.2307	$972.24	$972.30	$972.10