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	$211.28	12.825%	$238.3767	$238.38	$238.40	$238.40
Purchase #2	$82.32	9.197%	$89.891	$89.89	$89.90	$89.90
Purchase #3	$190.64	11.271%	$212.127	$212.13	$212.15	$212.10
Purchase #4	$184.91	13.247%	$209.405	$209.41	$209.40	$209.40
Purchase #5	$97.85	8.390%	$106.0596	$106.06	$106.05	$106.10
Purchase #6	$111.40	8.476%	$120.8423	$120.84	$120.85	$120.80
Purchase #7	$35.64	4.737%	$37.3283	$37.33	$37.35	$37.30
7 purchase totals =	$914.04		$1,014.0299	$1,014.04	$1,014.10	$1,014.00