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	$113.38	4.464%	$118.4413	$118.44	$118.45	$118.40
Purchase #2	$188.35	6.342%	$200.2952	$200.30	$200.30	$200.30
Purchase #3	$127.83	11.741%	$142.8385	$142.84	$142.85	$142.80
Purchase #4	$69.73	5.422%	$73.5108	$73.51	$73.50	$73.50
Purchase #5	$101.51	13.611%	$115.3265	$115.33	$115.35	$115.30
Purchase #6	$121.55	5.112%	$127.7636	$127.76	$127.75	$127.80
Purchase #7	$78.26	12.494%	$88.0378	$88.04	$88.05	$88.00
7 purchase totals =	$800.61		$866.2137	$866.22	$866.25	$866.10