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	$107.32	9.857%	$117.8985	$117.90	$117.90	$117.90
Purchase #2	$10.44	7.372%	$11.2096	$11.21	$11.20	$11.20
Purchase #3	$108.27	4.147%	$112.76	$112.76	$112.75	$112.80
Purchase #4	$28.38	11.256%	$31.5745	$31.57	$31.55	$31.60
Purchase #5	$55.91	9.535%	$61.241	$61.24	$61.25	$61.20
Purchase #6	$71.57	9.275%	$78.2081	$78.21	$78.20	$78.20
Purchase #7	$104.46	4.742%	$109.4135	$109.41	$109.40	$109.40
7 purchase totals =	$486.35		$522.3052	$522.30	$522.25	$522.30