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	$77.95	10.238%	$85.9305	$85.93	$85.95	$85.90
Purchase #2	$102.68	6.860%	$109.7238	$109.72	$109.70	$109.70
Purchase #3	$183.96	5.784%	$194.6002	$194.60	$194.60	$194.60
Purchase #4	$136.76	5.731%	$144.5977	$144.60	$144.60	$144.60
Purchase #5	$69.26	4.317%	$72.25	$72.25	$72.25	$72.30
Purchase #6	$157.58	6.680%	$168.1063	$168.11	$168.10	$168.10
Purchase #7	$54.27	7.865%	$58.5383	$58.54	$58.55	$58.50
7 purchase totals =	$782.46		$833.7468	$833.75	$833.75	$833.70