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	$43.29	7.717%	$46.6307	$46.63	$46.65	$46.60
Purchase #2	$45.89	4.483%	$47.9472	$47.95	$47.95	$47.90
Purchase #3	$126.95	7.417%	$136.3659	$136.37	$136.35	$136.40
Purchase #4	$6.46	4.235%	$6.7336	$6.73	$6.75	$6.70
Purchase #5	$41.27	13.319%	$46.7668	$46.77	$46.75	$46.80
Purchase #6	$168.27	12.670%	$189.5898	$189.59	$189.60	$189.60
Purchase #7	$52.65	13.741%	$59.8846	$59.88	$59.90	$59.90
7 purchase totals =	$484.78		$533.9186	$533.92	$533.95	$533.90