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	$190.94	6.156%	$202.6943	$202.69	$202.70	$202.70
Purchase #2	$19.31	6.762%	$20.6157	$20.62	$20.60	$20.60
Purchase #3	$219.47	12.346%	$246.5658	$246.57	$246.55	$246.60
Purchase #4	$183.98	7.840%	$198.404	$198.40	$198.40	$198.40
Purchase #5	$123.77	13.322%	$140.2586	$140.26	$140.25	$140.30
Purchase #6	$114.41	11.508%	$127.5763	$127.58	$127.60	$127.60
Purchase #7	$65.30	3.719%	$67.7285	$67.73	$67.75	$67.70
7 purchase totals =	$917.18		$1,003.8432	$1,003.85	$1,003.85	$1,003.90