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	$93.64	11.735%	$104.6287	$104.63	$104.65	$104.60
Purchase #2	$118.97	8.473%	$129.0503	$129.05	$129.05	$129.10
Purchase #3	$151.25	10.819%	$167.6137	$167.61	$167.60	$167.60
Purchase #4	$137.28	3.355%	$141.8857	$141.89	$141.90	$141.90
Purchase #5	$171.97	8.525%	$186.6304	$186.63	$186.65	$186.60
Purchase #6	$233.32	13.197%	$264.1112	$264.11	$264.10	$264.10
Purchase #7	$145.26	3.857%	$150.8627	$150.86	$150.85	$150.90
7 purchase totals =	$1,051.69		$1,144.7827	$1,144.78	$1,144.80	$1,144.80