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	$101.69	4.556%	$106.323	$106.32	$106.30	$106.30
Purchase #2	$128.77	10.740%	$142.5999	$142.60	$142.60	$142.60
Purchase #3	$129.26	6.521%	$137.689	$137.69	$137.70	$137.70
Purchase #4	$153.44	10.122%	$168.9712	$168.97	$168.95	$169.00
Purchase #5	$74.29	4.264%	$77.4577	$77.46	$77.45	$77.50
Purchase #6	$227.44	11.498%	$253.5911	$253.59	$253.60	$253.60
Purchase #7	$218.72	10.151%	$240.9223	$240.92	$240.90	$240.90
7 purchase totals =	$1,033.61		$1,127.5542	$1,127.55	$1,127.50	$1,127.60