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	$18.33	4.712%	$19.1937	$19.19	$19.20	$19.20
Purchase #2	$55.65	8.598%	$60.4348	$60.43	$60.45	$60.40
Purchase #3	$200.38	7.615%	$215.6389	$215.64	$215.65	$215.60
Purchase #4	$213.82	13.729%	$243.1753	$243.18	$243.20	$243.20
Purchase #5	$160.83	6.677%	$171.5686	$171.57	$171.55	$171.60
Purchase #6	$58.49	10.132%	$64.4162	$64.42	$64.40	$64.40
Purchase #7	$215.40	6.380%	$229.1425	$229.14	$229.15	$229.10
7 purchase totals =	$922.90		$1,003.5700	$1,003.57	$1,003.60	$1,003.50