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	$209.84	13.486%	$238.139	$238.14	$238.15	$238.10
Purchase #2	$97.39	13.859%	$110.8873	$110.89	$110.90	$110.90
Purchase #3	$146.36	10.726%	$162.0586	$162.06	$162.05	$162.10
Purchase #4	$185.76	11.395%	$206.9274	$206.93	$206.95	$206.90
Purchase #5	$90.26	6.314%	$95.959	$95.96	$95.95	$96.00
Purchase #6	$98.51	8.118%	$106.507	$106.51	$106.50	$106.50
Purchase #7	$95.87	10.174%	$105.6238	$105.62	$105.60	$105.60
7 purchase totals =	$923.99		$1,026.1021	$1,026.11	$1,026.10	$1,026.10