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	$42.74	3.194%	$44.1051	$44.11	$44.10	$44.10
Purchase #2	$105.32	6.780%	$112.4607	$112.46	$112.45	$112.50
Purchase #3	$18.99	3.339%	$19.6241	$19.62	$19.60	$19.60
Purchase #4	$67.29	7.704%	$72.474	$72.47	$72.45	$72.50
Purchase #5	$164.99	9.300%	$180.3341	$180.33	$180.35	$180.30
Purchase #6	$156.39	8.611%	$169.8567	$169.86	$169.85	$169.90
Purchase #7	$247.32	11.793%	$276.4864	$276.49	$276.50	$276.50
7 purchase totals =	$803.04		$875.3411	$875.34	$875.30	$875.40