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	$64.63	8.780%	$70.3045	$70.30	$70.30	$70.30
Purchase #2	$145.72	4.480%	$152.2483	$152.25	$152.25	$152.20
Purchase #3	$48.80	6.399%	$51.9227	$51.92	$51.90	$51.90
Purchase #4	$62.69	7.713%	$67.5253	$67.53	$67.55	$67.50
Purchase #5	$91.34	3.390%	$94.4364	$94.44	$94.45	$94.40
Purchase #6	$207.60	7.495%	$223.1596	$223.16	$223.15	$223.20
Purchase #7	$157.39	7.289%	$168.8622	$168.86	$168.85	$168.90
7 purchase totals =	$778.17		$828.4590	$828.46	$828.45	$828.40