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	$161.33	11.624%	$180.083	$180.08	$180.10	$180.10
Purchase #2	$131.67	10.827%	$145.9259	$145.93	$145.95	$145.90
Purchase #3	$177.95	5.160%	$187.1322	$187.13	$187.15	$187.10
Purchase #4	$237.28	11.817%	$265.3194	$265.32	$265.30	$265.30
Purchase #5	$39.98	7.230%	$42.8706	$42.87	$42.85	$42.90
Purchase #6	$171.29	10.783%	$189.7602	$189.76	$189.75	$189.80
Purchase #7	$52.72	4.204%	$54.9363	$54.94	$54.95	$54.90
7 purchase totals =	$972.22		$1,066.0276	$1,066.03	$1,066.05	$1,066.00