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	$80.29	10.790%	$88.9533	$88.95	$88.95	$89.00
Purchase #2	$82.44	7.775%	$88.8497	$88.85	$88.85	$88.80
Purchase #3	$156.91	3.586%	$162.5368	$162.54	$162.55	$162.50
Purchase #4	$199.94	3.341%	$206.62	$206.62	$206.60	$206.60
Purchase #5	$43.58	5.303%	$45.891	$45.89	$45.90	$45.90
Purchase #6	$176.92	4.858%	$185.5148	$185.51	$185.50	$185.50
Purchase #7	$191.48	11.271%	$213.0617	$213.06	$213.05	$213.10
7 purchase totals =	$931.56		$991.4273	$991.42	$991.40	$991.40