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	$62.35	8.174%	$67.4465	$67.45	$67.45	$67.40
Purchase #2	$50.26	3.221%	$51.8789	$51.88	$51.90	$51.90
Purchase #3	$128.56	3.687%	$133.3	$133.30	$133.30	$133.30
Purchase #4	$6.80	10.422%	$7.5087	$7.51	$7.50	$7.50
Purchase #5	$41.56	10.534%	$45.9379	$45.94	$45.95	$45.90
Purchase #6	$141.83	12.380%	$159.3886	$159.39	$159.40	$159.40
Purchase #7	$107.26	3.371%	$110.8757	$110.88	$110.90	$110.90
7 purchase totals =	$538.62		$576.3363	$576.35	$576.40	$576.30