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	$55.40	3.342%	$57.2515	$57.25	$57.25	$57.30
Purchase #2	$181.80	9.410%	$198.9074	$198.91	$198.90	$198.90
Purchase #3	$199.38	8.729%	$216.7839	$216.78	$216.80	$216.80
Purchase #4	$240.28	6.281%	$255.372	$255.37	$255.35	$255.40
Purchase #5	$100.65	3.240%	$103.9111	$103.91	$103.90	$103.90
Purchase #6	$201.59	5.308%	$212.2904	$212.29	$212.30	$212.30
Purchase #7	$85.64	4.553%	$89.5392	$89.54	$89.55	$89.50
7 purchase totals =	$1,064.74		$1,134.0555	$1,134.05	$1,134.05	$1,134.10