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	$174.34	6.256%	$185.2467	$185.25	$185.25	$185.20
Purchase #2	$58.43	12.565%	$65.7717	$65.77	$65.75	$65.80
Purchase #3	$222.90	7.867%	$240.4355	$240.44	$240.45	$240.40
Purchase #4	$155.90	13.551%	$177.026	$177.03	$177.05	$177.00
Purchase #5	$232.54	13.113%	$263.033	$263.03	$263.05	$263.00
Purchase #6	$186.40	7.775%	$200.8926	$200.89	$200.90	$200.90
Purchase #7	$82.90	11.346%	$92.3058	$92.31	$92.30	$92.30
7 purchase totals =	$1,113.41		$1,224.7113	$1,224.72	$1,224.75	$1,224.60