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	$130.31	11.295%	$145.0285	$145.03	$145.05	$145.00
Purchase #2	$105.98	3.343%	$109.5229	$109.52	$109.50	$109.50
Purchase #3	$20.57	7.740%	$22.1621	$22.16	$22.15	$22.20
Purchase #4	$246.28	7.815%	$265.5268	$265.53	$265.55	$265.50
Purchase #5	$173.78	3.500%	$179.8623	$179.86	$179.85	$179.90
Purchase #6	$45.36	4.689%	$47.4869	$47.49	$47.50	$47.50
Purchase #7	$59.88	10.841%	$66.3716	$66.37	$66.35	$66.40
7 purchase totals =	$782.16		$835.9611	$835.96	$835.95	$836.00