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	$174.29	6.275%	$185.2267	$185.23	$185.25	$185.20
Purchase #2	$105.55	13.434%	$119.7296	$119.73	$119.75	$119.70
Purchase #3	$69.52	9.731%	$76.285	$76.29	$76.30	$76.30
Purchase #4	$31.35	12.476%	$35.2612	$35.26	$35.25	$35.30
Purchase #5	$159.87	9.727%	$175.4206	$175.42	$175.40	$175.40
Purchase #6	$218.83	10.738%	$242.328	$242.33	$242.35	$242.30
Purchase #7	$250.82	6.168%	$266.2906	$266.29	$266.30	$266.30
7 purchase totals =	$1,010.23		$1,100.5417	$1,100.55	$1,100.60	$1,100.50