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	$73.59	3.526%	$76.1848	$76.18	$76.20	$76.20
Purchase #2	$144.26	4.279%	$150.4329	$150.43	$150.45	$150.40
Purchase #3	$198.54	11.305%	$220.9849	$220.98	$221.00	$221.00
Purchase #4	$188.25	4.468%	$196.661	$196.66	$196.65	$196.70
Purchase #5	$117.31	3.665%	$121.6094	$121.61	$121.60	$121.60
Purchase #6	$134.55	10.840%	$149.1352	$149.14	$149.15	$149.10
Purchase #7	$180.77	4.160%	$188.29	$188.29	$188.30	$188.30
7 purchase totals =	$1,037.27		$1,103.2982	$1,103.29	$1,103.35	$1,103.30