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	$126.72	5.380%	$133.5375	$133.54	$133.55	$133.50
Purchase #2	$26.73	7.544%	$28.7465	$28.75	$28.75	$28.70
Purchase #3	$242.49	3.463%	$250.8874	$250.89	$250.90	$250.90
Purchase #4	$219.33	13.173%	$248.2223	$248.22	$248.20	$248.20
Purchase #5	$74.51	12.317%	$83.6874	$83.69	$83.70	$83.70
Purchase #6	$83.45	8.538%	$90.575	$90.58	$90.60	$90.60
Purchase #7	$206.61	7.636%	$222.3867	$222.39	$222.40	$222.40
7 purchase totals =	$979.84		$1,058.0428	$1,058.06	$1,058.10	$1,058.00