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	$148.59	9.274%	$162.3702	$162.37	$162.35	$162.40
Purchase #2	$168.74	7.563%	$181.5018	$181.50	$181.50	$181.50
Purchase #3	$241.47	6.400%	$256.9241	$256.92	$256.90	$256.90
Purchase #4	$148.73	8.702%	$161.6725	$161.67	$161.65	$161.70
Purchase #5	$18.26	12.414%	$20.5268	$20.53	$20.55	$20.50
Purchase #6	$135.59	4.751%	$142.0319	$142.03	$142.05	$142.00
Purchase #7	$134.64	3.526%	$139.3874	$139.39	$139.40	$139.40
7 purchase totals =	$996.02		$1,064.4147	$1,064.41	$1,064.40	$1,064.40