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	$55.43	7.808%	$59.758	$59.76	$59.75	$59.80
Purchase #2	$191.96	13.856%	$218.558	$218.56	$218.55	$218.60
Purchase #3	$184.41	8.244%	$199.6128	$199.61	$199.60	$199.60
Purchase #4	$47.55	10.214%	$52.4068	$52.41	$52.40	$52.40
Purchase #5	$55.82	3.535%	$57.7932	$57.79	$57.80	$57.80
Purchase #6	$68.66	7.185%	$73.5932	$73.59	$73.60	$73.60
Purchase #7	$187.47	4.696%	$196.2736	$196.27	$196.25	$196.30
7 purchase totals =	$791.30		$857.9956	$857.99	$857.95	$858.10