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	$39.76	10.113%	$43.7809	$43.78	$43.80	$43.80
Purchase #2	$48.85	11.321%	$54.3803	$54.38	$54.40	$54.40
Purchase #3	$6.65	10.254%	$7.3319	$7.33	$7.35	$7.30
Purchase #4	$61.82	8.570%	$67.118	$67.12	$67.10	$67.10
Purchase #5	$222.32	5.848%	$235.3213	$235.32	$235.30	$235.30
Purchase #6	$141.68	7.202%	$151.8838	$151.88	$151.90	$151.90
Purchase #7	$182.32	7.135%	$195.3285	$195.33	$195.35	$195.30
7 purchase totals =	$703.40		$755.1447	$755.14	$755.20	$755.10