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	$227.40	4.791%	$238.2947	$238.29	$238.30	$238.30
Purchase #2	$18.38	12.112%	$20.6062	$20.61	$20.60	$20.60
Purchase #3	$164.88	12.412%	$185.3449	$185.34	$185.35	$185.30
Purchase #4	$37.79	6.629%	$40.2951	$40.30	$40.30	$40.30
Purchase #5	$197.51	9.265%	$215.8093	$215.81	$215.80	$215.80
Purchase #6	$80.61	4.164%	$83.9666	$83.97	$83.95	$84.00
Purchase #7	$234.25	13.575%	$266.0494	$266.05	$266.05	$266.00
7 purchase totals =	$960.82		$1,050.3662	$1,050.37	$1,050.35	$1,050.30