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	$49.55	11.529%	$55.2626	$55.26	$55.25	$55.30
Purchase #2	$248.67	6.215%	$264.1248	$264.12	$264.10	$264.10
Purchase #3	$223.67	5.703%	$236.4259	$236.43	$236.45	$236.40
Purchase #4	$151.76	4.813%	$159.0642	$159.06	$159.05	$159.10
Purchase #5	$144.69	13.618%	$164.3939	$164.39	$164.40	$164.40
Purchase #6	$28.60	8.575%	$31.0525	$31.05	$31.05	$31.10
Purchase #7	$146.62	6.743%	$156.5066	$156.51	$156.50	$156.50
7 purchase totals =	$993.56		$1,066.8305	$1,066.82	$1,066.80	$1,066.90