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	$164.52	4.112%	$171.2851	$171.29	$171.30	$171.30
Purchase #2	$118.51	7.410%	$127.2916	$127.29	$127.30	$127.30
Purchase #3	$105.74	5.321%	$111.3664	$111.37	$111.35	$111.40
Purchase #4	$250.62	6.372%	$266.5895	$266.59	$266.60	$266.60
Purchase #5	$185.56	6.473%	$197.5713	$197.57	$197.55	$197.60
Purchase #6	$156.43	3.336%	$161.6485	$161.65	$161.65	$161.60
Purchase #7	$61.46	13.311%	$69.6409	$69.64	$69.65	$69.60
7 purchase totals =	$1,042.84		$1,105.3933	$1,105.40	$1,105.40	$1,105.40