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	$134.55	12.863%	$151.8572	$151.86	$151.85	$151.90
Purchase #2	$159.95	7.831%	$172.4757	$172.48	$172.50	$172.50
Purchase #3	$88.95	11.494%	$99.1739	$99.17	$99.15	$99.20
Purchase #4	$248.69	8.607%	$270.0947	$270.09	$270.10	$270.10
Purchase #5	$83.38	6.751%	$89.009	$89.01	$89.00	$89.00
Purchase #6	$160.45	13.107%	$181.4802	$181.48	$181.50	$181.50
Purchase #7	$218.40	11.354%	$243.1971	$243.20	$243.20	$243.20
7 purchase totals =	$1,094.37		$1,207.2878	$1,207.29	$1,207.30	$1,207.40