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	$152.68	9.602%	$167.3403	$167.34	$167.35	$167.30
Purchase #2	$9.86	11.377%	$10.9818	$10.98	$11.00	$11.00
Purchase #3	$219.87	4.427%	$229.6036	$229.60	$229.60	$229.60
Purchase #4	$181.76	4.658%	$190.2264	$190.23	$190.25	$190.20
Purchase #5	$12.99	9.356%	$14.2053	$14.21	$14.20	$14.20
Purchase #6	$181.54	4.666%	$190.0107	$190.01	$190.00	$190.00
Purchase #7	$168.39	9.870%	$185.0101	$185.01	$185.00	$185.00
7 purchase totals =	$927.09		$987.3782	$987.38	$987.40	$987.30