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	$168.78	7.845%	$182.0208	$182.02	$182.00	$182.00
Purchase #2	$55.71	12.496%	$62.6715	$62.67	$62.65	$62.70
Purchase #3	$190.50	3.120%	$196.4436	$196.44	$196.45	$196.40
Purchase #4	$235.59	13.772%	$268.0355	$268.04	$268.05	$268.00
Purchase #5	$24.61	10.177%	$27.1146	$27.11	$27.10	$27.10
Purchase #6	$36.25	5.735%	$38.3289	$38.33	$38.35	$38.30
Purchase #7	$54.48	11.764%	$60.889	$60.89	$60.90	$60.90
7 purchase totals =	$765.92		$835.5039	$835.50	$835.50	$835.40