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	$119.74	5.333%	$126.1257	$126.13	$126.15	$126.10
Purchase #2	$42.58	4.288%	$44.4058	$44.41	$44.40	$44.40
Purchase #3	$250.68	5.735%	$265.0565	$265.06	$265.05	$265.10
Purchase #4	$34.41	11.476%	$38.3589	$38.36	$38.35	$38.40
Purchase #5	$245.47	13.229%	$277.9432	$277.94	$277.95	$277.90
Purchase #6	$175.86	11.509%	$196.0997	$196.10	$196.10	$196.10
Purchase #7	$48.30	10.304%	$53.2768	$53.28	$53.30	$53.30
7 purchase totals =	$917.04		$1,001.2666	$1,001.28	$1,001.30	$1,001.30