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	$77.44	10.615%	$85.6603	$85.66	$85.65	$85.70
Purchase #2	$144.98	9.315%	$158.4849	$158.48	$158.50	$158.50
Purchase #3	$235.47	6.378%	$250.4883	$250.49	$250.50	$250.50
Purchase #4	$92.76	11.692%	$103.6055	$103.61	$103.60	$103.60
Purchase #5	$181.82	11.870%	$203.402	$203.40	$203.40	$203.40
Purchase #6	$47.46	12.559%	$53.4205	$53.42	$53.40	$53.40
Purchase #7	$61.89	13.524%	$70.26	$70.26	$70.25	$70.30
7 purchase totals =	$841.82		$925.3215	$925.32	$925.30	$925.40