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	$250.37	10.282%	$276.113	$276.11	$276.10	$276.10
Purchase #2	$5.95	9.862%	$6.5368	$6.54	$6.55	$6.50
Purchase #3	$89.76	11.443%	$100.0312	$100.03	$100.05	$100.00
Purchase #4	$156.30	10.700%	$173.0241	$173.02	$173.00	$173.00
Purchase #5	$245.38	11.414%	$273.3877	$273.39	$273.40	$273.40
Purchase #6	$43.58	5.289%	$45.8849	$45.88	$45.90	$45.90
Purchase #7	$236.77	8.309%	$256.4432	$256.44	$256.45	$256.40
7 purchase totals =	$1,028.11		$1,131.4209	$1,131.41	$1,131.45	$1,131.30