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	$91.66	4.868%	$96.122	$96.12	$96.10	$96.10
Purchase #2	$109.84	12.767%	$123.8633	$123.86	$123.85	$123.90
Purchase #3	$247.44	6.271%	$262.957	$262.96	$262.95	$263.00
Purchase #4	$83.52	6.763%	$89.1685	$89.17	$89.15	$89.20
Purchase #5	$120.40	10.851%	$133.4646	$133.46	$133.45	$133.50
Purchase #6	$37.85	6.295%	$40.2327	$40.23	$40.25	$40.20
Purchase #7	$15.56	10.715%	$17.2273	$17.23	$17.25	$17.20
7 purchase totals =	$706.27		$763.0354	$763.03	$763.00	$763.10