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	$62.74	12.136%	$70.3541	$70.35	$70.35	$70.40
Purchase #2	$228.50	12.144%	$256.249	$256.25	$256.25	$256.20
Purchase #3	$250.94	8.444%	$272.1294	$272.13	$272.15	$272.10
Purchase #4	$216.55	3.607%	$224.361	$224.36	$224.35	$224.40
Purchase #5	$175.59	9.167%	$191.6863	$191.69	$191.70	$191.70
Purchase #6	$233.74	13.218%	$264.6358	$264.64	$264.65	$264.60
Purchase #7	$79.65	3.721%	$82.6138	$82.61	$82.60	$82.60
7 purchase totals =	$1,247.71		$1,362.0294	$1,362.03	$1,362.05	$1,362.00