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	$93.66	7.216%	$100.4185	$100.42	$100.40	$100.40
Purchase #2	$74.89	7.206%	$80.2866	$80.29	$80.30	$80.30
Purchase #3	$167.90	3.400%	$173.6086	$173.61	$173.60	$173.60
Purchase #4	$129.72	12.833%	$146.367	$146.37	$146.35	$146.40
Purchase #5	$49.96	3.153%	$51.5352	$51.54	$51.55	$51.50
Purchase #6	$113.58	8.338%	$123.0503	$123.05	$123.05	$123.10
Purchase #7	$162.97	6.834%	$174.1074	$174.11	$174.10	$174.10
7 purchase totals =	$792.68		$849.3736	$849.39	$849.35	$849.40