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	$160.74	13.270%	$182.0702	$182.07	$182.05	$182.10
Purchase #2	$91.88	5.164%	$96.6247	$96.62	$96.60	$96.60
Purchase #3	$144.66	9.378%	$158.2262	$158.23	$158.25	$158.20
Purchase #4	$100.65	13.856%	$114.5961	$114.60	$114.60	$114.60
Purchase #5	$168.99	6.683%	$180.2836	$180.28	$180.30	$180.30
Purchase #6	$228.28	6.576%	$243.2917	$243.29	$243.30	$243.30
Purchase #7	$79.73	13.873%	$90.7909	$90.79	$90.80	$90.80
7 purchase totals =	$974.93		$1,065.8834	$1,065.88	$1,065.90	$1,065.90