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	$189.26	3.590%	$196.0544	$196.05	$196.05	$196.10
Purchase #2	$233.65	4.121%	$243.2787	$243.28	$243.30	$243.30
Purchase #3	$42.99	11.447%	$47.9111	$47.91	$47.90	$47.90
Purchase #4	$55.65	11.196%	$61.8806	$61.88	$61.90	$61.90
Purchase #5	$63.50	5.470%	$66.9735	$66.97	$66.95	$67.00
Purchase #6	$131.46	10.693%	$145.517	$145.52	$145.50	$145.50
Purchase #7	$42.44	7.682%	$45.7002	$45.70	$45.70	$45.70
7 purchase totals =	$758.95		$807.3155	$807.31	$807.30	$807.40