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	$152.32	4.231%	$158.7647	$158.76	$158.75	$158.80
Purchase #2	$99.66	12.767%	$112.3836	$112.38	$112.40	$112.40
Purchase #3	$121.31	6.759%	$129.5093	$129.51	$129.50	$129.50
Purchase #4	$160.33	7.287%	$172.0132	$172.01	$172.00	$172.00
Purchase #5	$98.44	11.298%	$109.5618	$109.56	$109.55	$109.60
Purchase #6	$111.75	10.547%	$123.5363	$123.54	$123.55	$123.50
Purchase #7	$7.43	5.357%	$7.828	$7.83	$7.85	$7.80
7 purchase totals =	$751.24		$813.5969	$813.59	$813.60	$813.60