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	$147.87	6.780%	$157.8956	$157.90	$157.90	$157.90
Purchase #2	$54.98	8.287%	$59.5362	$59.54	$59.55	$59.50
Purchase #3	$191.39	5.665%	$202.2322	$202.23	$202.25	$202.20
Purchase #4	$152.52	6.685%	$162.716	$162.72	$162.70	$162.70
Purchase #5	$117.45	3.162%	$121.1638	$121.16	$121.15	$121.20
Purchase #6	$143.82	9.801%	$157.9158	$157.92	$157.90	$157.90
Purchase #7	$225.88	10.559%	$249.7307	$249.73	$249.75	$249.70
7 purchase totals =	$1,033.91		$1,111.1903	$1,111.20	$1,111.20	$1,111.10