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	5.283%	$101.0401	$101.04	$101.05	$101.00
Purchase #2	$98.57	9.612%	$108.0445	$108.04	$108.05	$108.00
Purchase #3	$37.61	11.695%	$42.0085	$42.01	$42.00	$42.00
Purchase #4	$64.96	11.433%	$72.3869	$72.39	$72.40	$72.40
Purchase #5	$55.85	9.674%	$61.2529	$61.25	$61.25	$61.30
Purchase #6	$74.90	10.766%	$82.9637	$82.96	$82.95	$83.00
Purchase #7	$198.43	13.365%	$224.9502	$224.95	$224.95	$225.00
7 purchase totals =	$626.29		$692.6468	$692.64	$692.65	$692.70