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	$224.75	11.355%	$250.2704	$250.27	$250.25	$250.30
Purchase #2	$45.44	6.268%	$48.2882	$48.29	$48.30	$48.30
Purchase #3	$138.67	9.108%	$151.3001	$151.30	$151.30	$151.30
Purchase #4	$198.30	13.765%	$225.596	$225.60	$225.60	$225.60
Purchase #5	$211.83	5.329%	$223.1184	$223.12	$223.10	$223.10
Purchase #6	$189.55	11.254%	$210.882	$210.88	$210.90	$210.90
Purchase #7	$73.83	13.111%	$83.5099	$83.51	$83.50	$83.50
7 purchase totals =	$1,082.37		$1,192.9650	$1,192.97	$1,192.95	$1,193.00