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	$215.59	3.549%	$223.2413	$223.24	$223.25	$223.20
Purchase #2	$244.32	4.274%	$254.7622	$254.76	$254.75	$254.80
Purchase #3	$35.39	13.555%	$40.1871	$40.19	$40.20	$40.20
Purchase #4	$237.83	9.688%	$260.871	$260.87	$260.85	$260.90
Purchase #5	$211.55	9.778%	$232.2354	$232.24	$232.25	$232.20
Purchase #6	$46.77	13.865%	$53.2547	$53.25	$53.25	$53.30
Purchase #7	$82.44	9.390%	$90.1811	$90.18	$90.20	$90.20
7 purchase totals =	$1,073.89		$1,154.7328	$1,154.73	$1,154.75	$1,154.80