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	$101.64	3.766%	$105.4678	$105.47	$105.45	$105.50
Purchase #2	$139.58	6.838%	$149.1245	$149.12	$149.10	$149.10
Purchase #3	$125.90	4.117%	$131.0833	$131.08	$131.10	$131.10
Purchase #4	$37.82	5.809%	$40.017	$40.02	$40.00	$40.00
Purchase #5	$162.47	13.115%	$183.7779	$183.78	$183.80	$183.80
Purchase #6	$78.40	13.218%	$88.7629	$88.76	$88.75	$88.80
Purchase #7	$105.53	3.581%	$109.309	$109.31	$109.30	$109.30
7 purchase totals =	$751.34		$807.5424	$807.54	$807.50	$807.60