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	$64.73	10.681%	$71.6438	$71.64	$71.65	$71.60
Purchase #2	$36.74	7.776%	$39.5969	$39.60	$39.60	$39.60
Purchase #3	$208.73	9.281%	$228.1022	$228.10	$228.10	$228.10
Purchase #4	$101.57	13.819%	$115.606	$115.61	$115.60	$115.60
Purchase #5	$104.52	3.658%	$108.3433	$108.34	$108.35	$108.30
Purchase #6	$93.91	7.347%	$100.8096	$100.81	$100.80	$100.80
Purchase #7	$48.60	11.376%	$54.1287	$54.13	$54.15	$54.10
7 purchase totals =	$658.80		$718.2305	$718.23	$718.25	$718.10