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	$126.36	5.442%	$133.2365	$133.24	$133.25	$133.20
Purchase #2	$100.34	11.520%	$111.8992	$111.90	$111.90	$111.90
Purchase #3	$167.76	10.811%	$185.8965	$185.90	$185.90	$185.90
Purchase #4	$227.60	6.388%	$242.1391	$242.14	$242.15	$242.10
Purchase #5	$72.72	7.578%	$78.2307	$78.23	$78.25	$78.20
Purchase #6	$221.27	7.736%	$238.3874	$238.39	$238.40	$238.40
Purchase #7	$35.97	4.252%	$37.4994	$37.50	$37.50	$37.50
7 purchase totals =	$952.02		$1,027.2888	$1,027.30	$1,027.35	$1,027.20