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	$96.42	4.718%	$100.9691	$100.97	$100.95	$101.00
Purchase #2	$105.56	3.359%	$109.1058	$109.11	$109.10	$109.10
Purchase #3	$81.32	3.185%	$83.91	$83.91	$83.90	$83.90
Purchase #4	$234.45	4.283%	$244.4915	$244.49	$244.50	$244.50
Purchase #5	$93.65	13.732%	$106.51	$106.51	$106.50	$106.50
Purchase #6	$78.48	3.208%	$80.9976	$81.00	$81.00	$81.00
Purchase #7	$52.47	6.485%	$55.8727	$55.87	$55.85	$55.90
7 purchase totals =	$742.35		$781.8567	$781.86	$781.80	$781.90