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	$184.64	6.645%	$196.9093	$196.91	$196.90	$196.90
Purchase #2	$31.92	8.597%	$34.6642	$34.66	$34.65	$34.70
Purchase #3	$131.93	10.335%	$145.565	$145.57	$145.55	$145.60
Purchase #4	$176.52	13.514%	$200.3749	$200.37	$200.35	$200.40
Purchase #5	$98.45	6.687%	$105.0334	$105.03	$105.05	$105.00
Purchase #6	$201.56	7.283%	$216.2396	$216.24	$216.25	$216.20
Purchase #7	$129.63	13.786%	$147.5008	$147.50	$147.50	$147.50
7 purchase totals =	$954.65		$1,046.2872	$1,046.28	$1,046.25	$1,046.30