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	$25.72	10.345%	$28.3807	$28.38	$28.40	$28.40
Purchase #2	$168.59	9.731%	$184.9955	$185.00	$185.00	$185.00
Purchase #3	$195.94	3.541%	$202.8782	$202.88	$202.90	$202.90
Purchase #4	$78.89	10.665%	$87.3036	$87.30	$87.30	$87.30
Purchase #5	$169.73	3.377%	$175.4618	$175.46	$175.45	$175.50
Purchase #6	$212.87	4.264%	$221.9468	$221.95	$221.95	$221.90
Purchase #7	$153.85	4.175%	$160.2732	$160.27	$160.25	$160.30
7 purchase totals =	$1,005.59		$1,061.2398	$1,061.24	$1,061.25	$1,061.30