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	$179.79	13.712%	$204.4428	$204.44	$204.45	$204.40
Purchase #2	$230.58	13.302%	$261.2518	$261.25	$261.25	$261.30
Purchase #3	$46.63	4.419%	$48.6906	$48.69	$48.70	$48.70
Purchase #4	$91.78	12.361%	$103.1249	$103.12	$103.10	$103.10
Purchase #5	$116.75	9.418%	$127.7455	$127.75	$127.75	$127.70
Purchase #6	$172.45	7.654%	$185.6493	$185.65	$185.65	$185.60
Purchase #7	$192.26	9.459%	$210.4459	$210.45	$210.45	$210.40
7 purchase totals =	$1,030.24		$1,141.3508	$1,141.35	$1,141.35	$1,141.20