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	$47.63	3.184%	$49.1465	$49.15	$49.15	$49.10
Purchase #2	$60.91	10.342%	$67.2093	$67.21	$67.20	$67.20
Purchase #3	$99.28	12.727%	$111.9154	$111.92	$111.90	$111.90
Purchase #4	$42.66	10.507%	$47.1423	$47.14	$47.15	$47.10
Purchase #5	$125.85	12.453%	$141.5221	$141.52	$141.50	$141.50
Purchase #6	$44.71	12.463%	$50.2822	$50.28	$50.30	$50.30
Purchase #7	$81.56	6.867%	$87.1607	$87.16	$87.15	$87.20
7 purchase totals =	$502.60		$554.3785	$554.38	$554.35	$554.30