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	$166.28	3.414%	$171.9568	$171.96	$171.95	$172.00
Purchase #2	$17.25	5.565%	$18.21	$18.21	$18.20	$18.20
Purchase #3	$55.41	7.470%	$59.5491	$59.55	$59.55	$59.50
Purchase #4	$74.25	8.477%	$80.5442	$80.54	$80.55	$80.50
Purchase #5	$86.50	3.277%	$89.3346	$89.33	$89.35	$89.30
Purchase #6	$209.35	13.787%	$238.2131	$238.21	$238.20	$238.20
Purchase #7	$196.28	6.678%	$209.3876	$209.39	$209.40	$209.40
7 purchase totals =	$805.32		$867.1954	$867.19	$867.20	$867.10