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	$144.38	7.248%	$154.8447	$154.84	$154.85	$154.80
Purchase #2	$177.64	4.749%	$186.0761	$186.08	$186.10	$186.10
Purchase #3	$229.99	10.142%	$253.3156	$253.32	$253.30	$253.30
Purchase #4	$72.88	6.710%	$77.7702	$77.77	$77.75	$77.80
Purchase #5	$78.39	10.345%	$86.4994	$86.50	$86.50	$86.50
Purchase #6	$59.38	8.438%	$64.3905	$64.39	$64.40	$64.40
Purchase #7	$181.89	4.361%	$189.8222	$189.82	$189.80	$189.80
7 purchase totals =	$944.55		$1,012.7187	$1,012.72	$1,012.70	$1,012.70