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	$130.87	11.142%	$145.4515	$145.45	$145.45	$145.50
Purchase #2	$78.37	11.689%	$87.5307	$87.53	$87.55	$87.50
Purchase #3	$139.92	11.735%	$156.3396	$156.34	$156.35	$156.30
Purchase #4	$126.37	11.179%	$140.4969	$140.50	$140.50	$140.50
Purchase #5	$220.28	7.780%	$237.4178	$237.42	$237.40	$237.40
Purchase #6	$116.76	9.279%	$127.5942	$127.59	$127.60	$127.60
Purchase #7	$18.55	6.501%	$19.7559	$19.76	$19.75	$19.80
7 purchase totals =	$831.12		$914.5866	$914.59	$914.60	$914.60