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	$231.38	12.176%	$259.5528	$259.55	$259.55	$259.60
Purchase #2	$64.71	3.583%	$67.0286	$67.03	$67.05	$67.00
Purchase #3	$7.74	8.829%	$8.4234	$8.42	$8.40	$8.40
Purchase #4	$64.56	13.568%	$73.3195	$73.32	$73.30	$73.30
Purchase #5	$71.52	11.550%	$79.7806	$79.78	$79.80	$79.80
Purchase #6	$55.90	5.788%	$59.1355	$59.14	$59.15	$59.10
Purchase #7	$154.73	13.104%	$175.0058	$175.01	$175.00	$175.00
7 purchase totals =	$650.54		$722.2462	$722.25	$722.25	$722.20