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	$77.41	11.721%	$86.4832	$86.48	$86.50	$86.50
Purchase #2	$72.32	9.461%	$79.1622	$79.16	$79.15	$79.20
Purchase #3	$67.56	7.681%	$72.7493	$72.75	$72.75	$72.70
Purchase #4	$55.51	12.549%	$62.4759	$62.48	$62.50	$62.50
Purchase #5	$133.39	5.369%	$140.5517	$140.55	$140.55	$140.60
Purchase #6	$55.86	3.730%	$57.9436	$57.94	$57.95	$57.90
Purchase #7	$184.92	11.270%	$205.7605	$205.76	$205.75	$205.80
7 purchase totals =	$646.97		$705.1264	$705.12	$705.15	$705.20