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	$76.67	7.459%	$82.3888	$82.39	$82.40	$82.40
Purchase #2	$180.48	5.589%	$190.567	$190.57	$190.55	$190.60
Purchase #3	$9.85	3.780%	$10.2223	$10.22	$10.20	$10.20
Purchase #4	$144.99	10.711%	$160.5199	$160.52	$160.50	$160.50
Purchase #5	$38.27	8.343%	$41.4629	$41.46	$41.45	$41.50
Purchase #6	$28.26	9.639%	$30.984	$30.98	$31.00	$31.00
Purchase #7	$168.95	6.217%	$179.4536	$179.45	$179.45	$179.50
7 purchase totals =	$647.47		$695.5985	$695.59	$695.55	$695.70