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	$159.71	8.391%	$173.1113	$173.11	$173.10	$173.10
Purchase #2	$91.88	8.681%	$99.8561	$99.86	$99.85	$99.90
Purchase #3	$215.91	7.175%	$231.4015	$231.40	$231.40	$231.40
Purchase #4	$156.73	3.689%	$162.5118	$162.51	$162.50	$162.50
Purchase #5	$114.98	7.471%	$123.5702	$123.57	$123.55	$123.60
Purchase #6	$116.53	13.715%	$132.5121	$132.51	$132.50	$132.50
Purchase #7	$227.31	3.323%	$234.8635	$234.86	$234.85	$234.90
7 purchase totals =	$1,083.05		$1,157.8265	$1,157.82	$1,157.75	$1,157.90