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	$58.76	10.710%	$65.0532	$65.05	$65.05	$65.10
Purchase #2	$115.74	13.467%	$131.3267	$131.33	$131.35	$131.30
Purchase #3	$103.31	3.397%	$106.8194	$106.82	$106.80	$106.80
Purchase #4	$52.61	5.402%	$55.452	$55.45	$55.45	$55.50
Purchase #5	$66.57	10.434%	$73.5159	$73.52	$73.50	$73.50
Purchase #6	$170.65	4.164%	$177.7559	$177.76	$177.75	$177.80
Purchase #7	$47.63	12.331%	$53.5033	$53.50	$53.50	$53.50
7 purchase totals =	$615.27		$663.4264	$663.43	$663.40	$663.50