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	$95.97	7.353%	$103.0267	$103.03	$103.05	$103.00
Purchase #2	$17.89	3.771%	$18.5646	$18.56	$18.55	$18.60
Purchase #3	$31.49	10.344%	$34.7473	$34.75	$34.75	$34.70
Purchase #4	$64.79	11.515%	$72.2506	$72.25	$72.25	$72.30
Purchase #5	$172.86	6.612%	$184.2895	$184.29	$184.30	$184.30
Purchase #6	$137.27	11.146%	$152.5701	$152.57	$152.55	$152.60
Purchase #7	$106.74	13.287%	$120.9225	$120.92	$120.90	$120.90
7 purchase totals =	$627.01		$686.3713	$686.37	$686.35	$686.40