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	$197.39	9.144%	$215.4393	$215.44	$215.45	$215.40
Purchase #2	$19.94	3.271%	$20.5922	$20.59	$20.60	$20.60
Purchase #3	$169.47	9.400%	$185.4002	$185.40	$185.40	$185.40
Purchase #4	$61.50	9.309%	$67.225	$67.23	$67.25	$67.20
Purchase #5	$170.83	12.850%	$192.7817	$192.78	$192.80	$192.80
Purchase #6	$10.94	10.484%	$12.0869	$12.09	$12.10	$12.10
Purchase #7	$237.38	7.597%	$255.4138	$255.41	$255.40	$255.40
7 purchase totals =	$867.45		$948.9391	$948.94	$949.00	$948.90