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	$100.56	4.718%	$105.3044	$105.30	$105.30	$105.30
Purchase #2	$247.69	10.294%	$273.1872	$273.19	$273.20	$273.20
Purchase #3	$47.46	8.370%	$51.4324	$51.43	$51.45	$51.40
Purchase #4	$250.34	10.359%	$276.2727	$276.27	$276.25	$276.30
Purchase #5	$90.44	5.384%	$95.3093	$95.31	$95.30	$95.30
Purchase #6	$123.46	11.478%	$137.6307	$137.63	$137.65	$137.60
Purchase #7	$25.92	6.618%	$27.6354	$27.64	$27.65	$27.60
7 purchase totals =	$885.87		$966.7721	$966.77	$966.80	$966.70