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	$125.57	4.270%	$130.9318	$130.93	$130.95	$130.90
Purchase #2	$161.88	7.700%	$174.3448	$174.34	$174.35	$174.30
Purchase #3	$230.58	5.736%	$243.8061	$243.81	$243.80	$243.80
Purchase #4	$42.43	6.677%	$45.2631	$45.26	$45.25	$45.30
Purchase #5	$159.58	12.571%	$179.6408	$179.64	$179.65	$179.60
Purchase #6	$37.45	8.789%	$40.7415	$40.74	$40.75	$40.70
Purchase #7	$239.38	4.581%	$250.346	$250.35	$250.35	$250.30
7 purchase totals =	$996.87		$1,065.0741	$1,065.07	$1,065.10	$1,064.90