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	$200.80	7.865%	$216.5929	$216.59	$216.60	$216.60
Purchase #2	$84.93	13.333%	$96.2537	$96.25	$96.25	$96.30
Purchase #3	$128.89	12.282%	$144.7203	$144.72	$144.70	$144.70
Purchase #4	$188.48	13.280%	$213.5101	$213.51	$213.50	$213.50
Purchase #5	$53.83	10.147%	$59.2921	$59.29	$59.30	$59.30
Purchase #6	$118.37	4.827%	$124.0837	$124.08	$124.10	$124.10
Purchase #7	$136.88	7.668%	$147.376	$147.38	$147.40	$147.40
7 purchase totals =	$912.18		$1,001.8288	$1,001.82	$1,001.85	$1,001.90