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	$196.95	11.225%	$219.0576	$219.06	$219.05	$219.10
Purchase #2	$109.46	12.399%	$123.0319	$123.03	$123.05	$123.00
Purchase #3	$39.38	3.752%	$40.8575	$40.86	$40.85	$40.90
Purchase #4	$47.89	9.375%	$52.3797	$52.38	$52.40	$52.40
Purchase #5	$51.90	11.287%	$57.758	$57.76	$57.75	$57.80
Purchase #6	$133.26	8.237%	$144.2366	$144.24	$144.25	$144.20
Purchase #7	$26.49	11.546%	$29.5485	$29.55	$29.55	$29.50
7 purchase totals =	$605.33		$666.8698	$666.88	$666.90	$666.90