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	$95.52	11.366%	$106.3768	$106.38	$106.40	$106.40
Purchase #2	$70.28	11.532%	$78.3847	$78.38	$78.40	$78.40
Purchase #3	$186.35	4.320%	$194.4003	$194.40	$194.40	$194.40
Purchase #4	$69.31	8.781%	$75.3961	$75.40	$75.40	$75.40
Purchase #5	$115.45	3.760%	$119.7909	$119.79	$119.80	$119.80
Purchase #6	$90.47	9.790%	$99.327	$99.33	$99.35	$99.30
Purchase #7	$31.48	13.797%	$35.8233	$35.82	$35.80	$35.80
7 purchase totals =	$658.86		$709.4991	$709.50	$709.55	$709.50