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	$116.35	9.705%	$127.6418	$127.64	$127.65	$127.60
Purchase #2	$151.63	10.525%	$167.5891	$167.59	$167.60	$167.60
Purchase #3	$48.64	3.810%	$50.4932	$50.49	$50.50	$50.50
Purchase #4	$168.38	6.520%	$179.3584	$179.36	$179.35	$179.40
Purchase #5	$206.56	7.555%	$222.1656	$222.17	$222.15	$222.20
Purchase #6	$106.88	3.403%	$110.5171	$110.52	$110.50	$110.50
Purchase #7	$46.52	12.417%	$52.2964	$52.30	$52.30	$52.30
7 purchase totals =	$844.96		$910.0616	$910.07	$910.05	$910.10