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	$100.33	8.342%	$108.6995	$108.70	$108.70	$108.70
Purchase #2	$40.45	11.690%	$45.1786	$45.18	$45.20	$45.20
Purchase #3	$195.46	6.459%	$208.0848	$208.08	$208.10	$208.10
Purchase #4	$69.56	11.439%	$77.517	$77.52	$77.50	$77.50
Purchase #5	$151.52	3.485%	$156.8005	$156.80	$156.80	$156.80
Purchase #6	$90.35	4.615%	$94.5197	$94.52	$94.50	$94.50
Purchase #7	$103.77	5.303%	$109.2729	$109.27	$109.25	$109.30
7 purchase totals =	$751.44		$800.0730	$800.07	$800.05	$800.10