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	$100.59	9.542%	$110.1883	$110.19	$110.20	$110.20
Purchase #2	$234.86	4.337%	$245.0459	$245.05	$245.05	$245.00
Purchase #3	$237.67	7.137%	$254.6325	$254.63	$254.65	$254.60
Purchase #4	$94.90	4.332%	$99.0111	$99.01	$99.00	$99.00
Purchase #5	$243.43	3.465%	$251.8648	$251.86	$251.85	$251.90
Purchase #6	$81.66	11.312%	$90.8974	$90.90	$90.90	$90.90
Purchase #7	$155.65	7.477%	$167.288	$167.29	$167.30	$167.30
7 purchase totals =	$1,148.76		$1,218.9280	$1,218.93	$1,218.95	$1,218.90