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	$206.29	12.600%	$232.2825	$232.28	$232.30	$232.30
Purchase #2	$75.74	6.324%	$80.5298	$80.53	$80.55	$80.50
Purchase #3	$213.43	4.498%	$223.0301	$223.03	$223.05	$223.00
Purchase #4	$78.97	13.305%	$89.477	$89.48	$89.50	$89.50
Purchase #5	$113.47	12.575%	$127.7389	$127.74	$127.75	$127.70
Purchase #6	$182.96	4.728%	$191.6103	$191.61	$191.60	$191.60
Purchase #7	$218.45	4.475%	$228.2256	$228.23	$228.25	$228.20
7 purchase totals =	$1,089.31		$1,172.8942	$1,172.90	$1,173.00	$1,172.80