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	$218.86	10.563%	$241.9782	$241.98	$242.00	$242.00
Purchase #2	$237.87	6.472%	$253.2649	$253.26	$253.25	$253.30
Purchase #3	$187.46	9.498%	$205.265	$205.27	$205.25	$205.30
Purchase #4	$68.87	5.442%	$72.6179	$72.62	$72.60	$72.60
Purchase #5	$12.94	11.374%	$14.4118	$14.41	$14.40	$14.40
Purchase #6	$244.86	11.515%	$273.0556	$273.06	$273.05	$273.10
Purchase #7	$35.83	3.415%	$37.0536	$37.05	$37.05	$37.10
7 purchase totals =	$1,006.69		$1,097.6470	$1,097.65	$1,097.60	$1,097.80