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	$21.29	3.235%	$21.9787	$21.98	$22.00	$22.00
Purchase #2	$55.96	5.478%	$59.0255	$59.03	$59.05	$59.00
Purchase #3	$71.92	7.497%	$77.3118	$77.31	$77.30	$77.30
Purchase #4	$98.65	13.133%	$111.6057	$111.61	$111.60	$111.60
Purchase #5	$112.86	13.377%	$127.9573	$127.96	$127.95	$128.00
Purchase #6	$30.67	6.365%	$32.6221	$32.62	$32.60	$32.60
Purchase #7	$221.41	13.225%	$250.6915	$250.69	$250.70	$250.70
7 purchase totals =	$612.76		$681.1926	$681.20	$681.20	$681.20