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	$202.31	13.137%	$228.8875	$228.89	$228.90	$228.90
Purchase #2	$32.48	9.451%	$35.5497	$35.55	$35.55	$35.50
Purchase #3	$223.92	13.646%	$254.4761	$254.48	$254.50	$254.50
Purchase #4	$120.25	8.155%	$130.0564	$130.06	$130.05	$130.10
Purchase #5	$213.91	7.333%	$229.596	$229.60	$229.60	$229.60
Purchase #6	$77.96	4.382%	$81.3762	$81.38	$81.40	$81.40
Purchase #7	$204.89	10.540%	$226.4854	$226.49	$226.50	$226.50
7 purchase totals =	$1,075.72		$1,186.4273	$1,186.45	$1,186.50	$1,186.50