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	$79.53	3.398%	$82.2324	$82.23	$82.25	$82.20
Purchase #2	$68.96	5.328%	$72.6342	$72.63	$72.65	$72.60
Purchase #3	$98.59	8.117%	$106.5926	$106.59	$106.60	$106.60
Purchase #4	$248.84	13.707%	$282.9485	$282.95	$282.95	$282.90
Purchase #5	$165.57	8.736%	$180.0342	$180.03	$180.05	$180.00
Purchase #6	$46.40	9.791%	$50.943	$50.94	$50.95	$50.90
Purchase #7	$167.92	10.507%	$185.5634	$185.56	$185.55	$185.60
7 purchase totals =	$875.81		$960.9483	$960.93	$961.00	$960.80