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	$62.85	10.142%	$69.2242	$69.22	$69.20	$69.20
Purchase #2	$77.46	11.753%	$86.5639	$86.56	$86.55	$86.60
Purchase #3	$101.34	11.829%	$113.3275	$113.33	$113.35	$113.30
Purchase #4	$183.60	9.153%	$200.4049	$200.40	$200.40	$200.40
Purchase #5	$41.39	9.705%	$45.4069	$45.41	$45.40	$45.40
Purchase #6	$168.37	11.869%	$188.3538	$188.35	$188.35	$188.40
Purchase #7	$58.88	3.106%	$60.7088	$60.71	$60.70	$60.70
7 purchase totals =	$693.89		$763.9900	$763.98	$763.95	$764.00