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	$48.69	11.596%	$54.3361	$54.34	$54.35	$54.30
Purchase #2	$213.81	7.518%	$229.8842	$229.88	$229.90	$229.90
Purchase #3	$10.61	4.320%	$11.0684	$11.07	$11.05	$11.10
Purchase #4	$82.85	13.653%	$94.1615	$94.16	$94.15	$94.20
Purchase #5	$237.76	13.586%	$270.0621	$270.06	$270.05	$270.10
Purchase #6	$59.90	3.323%	$61.8905	$61.89	$61.90	$61.90
Purchase #7	$12.97	5.354%	$13.6644	$13.66	$13.65	$13.70
7 purchase totals =	$666.59		$735.0672	$735.06	$735.05	$735.20