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	$14.95	5.270%	$15.7379	$15.74	$15.75	$15.70
Purchase #2	$19.64	4.760%	$20.5749	$20.57	$20.55	$20.60
Purchase #3	$92.77	13.295%	$105.1038	$105.10	$105.10	$105.10
Purchase #4	$88.92	7.404%	$95.5036	$95.50	$95.50	$95.50
Purchase #5	$44.53	6.799%	$47.5576	$47.56	$47.55	$47.60
Purchase #6	$38.75	9.549%	$42.4502	$42.45	$42.45	$42.50
Purchase #7	$172.75	9.569%	$189.2804	$189.28	$189.30	$189.30
7 purchase totals =	$472.31		$516.2084	$516.20	$516.20	$516.30