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	$76.35	12.534%	$85.9197	$85.92	$85.90	$85.90
Purchase #2	$79.52	13.433%	$90.2019	$90.20	$90.20	$90.20
Purchase #3	$31.55	4.836%	$33.0758	$33.08	$33.10	$33.10
Purchase #4	$67.72	6.784%	$72.3141	$72.31	$72.30	$72.30
Purchase #5	$65.73	10.701%	$72.7638	$72.76	$72.75	$72.80
Purchase #6	$72.26	7.435%	$77.6325	$77.63	$77.65	$77.60
Purchase #7	$40.36	12.636%	$45.4599	$45.46	$45.45	$45.50
7 purchase totals =	$433.49		$477.3677	$477.36	$477.35	$477.40