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	$53.72	3.752%	$55.7356	$55.74	$55.75	$55.70
Purchase #2	$174.44	3.127%	$179.8947	$179.89	$179.90	$179.90
Purchase #3	$39.83	4.136%	$41.4774	$41.48	$41.50	$41.50
Purchase #4	$138.78	5.632%	$146.5961	$146.60	$146.60	$146.60
Purchase #5	$149.62	6.543%	$159.4096	$159.41	$159.40	$159.40
Purchase #6	$53.56	8.341%	$58.0274	$58.03	$58.05	$58.00
Purchase #7	$66.98	7.705%	$72.1408	$72.14	$72.15	$72.10
7 purchase totals =	$676.93		$713.2816	$713.29	$713.35	$713.20