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	$237.74	3.254%	$245.4761	$245.48	$245.50	$245.50
Purchase #2	$62.69	11.329%	$69.7922	$69.79	$69.80	$69.80
Purchase #3	$33.69	11.112%	$37.4336	$37.43	$37.45	$37.40
Purchase #4	$48.84	7.444%	$52.4756	$52.48	$52.50	$52.50
Purchase #5	$86.40	3.293%	$89.2452	$89.25	$89.25	$89.20
Purchase #6	$203.78	11.783%	$227.7914	$227.79	$227.80	$227.80
Purchase #7	$149.96	8.333%	$162.4562	$162.46	$162.45	$162.50
7 purchase totals =	$823.10		$884.6703	$884.68	$884.75	$884.70