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	$159.62	8.320%	$172.9004	$172.90	$172.90	$172.90
Purchase #2	$10.27	11.538%	$11.455	$11.46	$11.45	$11.50
Purchase #3	$31.38	3.874%	$32.5957	$32.60	$32.60	$32.60
Purchase #4	$182.44	4.793%	$191.1843	$191.18	$191.20	$191.20
Purchase #5	$213.53	3.826%	$221.6997	$221.70	$221.70	$221.70
Purchase #6	$89.73	12.870%	$101.2783	$101.28	$101.30	$101.30
Purchase #7	$113.32	12.392%	$127.3626	$127.36	$127.35	$127.40
7 purchase totals =	$800.29		$858.4760	$858.48	$858.50	$858.60