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	$131.58	12.697%	$148.2867	$148.29	$148.30	$148.30
Purchase #2	$135.85	9.282%	$148.4596	$148.46	$148.45	$148.50
Purchase #3	$224.98	7.187%	$241.1493	$241.15	$241.15	$241.10
Purchase #4	$232.80	11.610%	$259.8281	$259.83	$259.85	$259.80
Purchase #5	$83.81	6.583%	$89.3272	$89.33	$89.35	$89.30
Purchase #6	$141.92	11.523%	$158.2734	$158.27	$158.25	$158.30
Purchase #7	$86.25	5.715%	$91.1792	$91.18	$91.20	$91.20
7 purchase totals =	$1,037.19		$1,136.5035	$1,136.51	$1,136.55	$1,136.50