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	$174.84	4.124%	$182.0504	$182.05	$182.05	$182.10
Purchase #2	$51.38	6.794%	$54.8708	$54.87	$54.85	$54.90
Purchase #3	$79.69	13.113%	$90.1397	$90.14	$90.15	$90.10
Purchase #4	$68.96	9.796%	$75.7153	$75.72	$75.70	$75.70
Purchase #5	$162.34	6.158%	$172.3369	$172.34	$172.35	$172.30
Purchase #6	$151.64	8.760%	$164.9237	$164.92	$164.90	$164.90
Purchase #7	$164.56	5.294%	$173.2718	$173.27	$173.25	$173.30
7 purchase totals =	$853.41		$913.3086	$913.31	$913.25	$913.30