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	$77.58	6.115%	$82.324	$82.32	$82.30	$82.30
Purchase #2	$78.46	12.280%	$88.0949	$88.09	$88.10	$88.10
Purchase #3	$179.32	4.849%	$188.0152	$188.02	$188.00	$188.00
Purchase #4	$47.54	12.247%	$53.3622	$53.36	$53.35	$53.40
Purchase #5	$206.71	3.276%	$213.4818	$213.48	$213.50	$213.50
Purchase #6	$249.57	4.143%	$259.9097	$259.91	$259.90	$259.90
Purchase #7	$151.47	7.278%	$162.494	$162.49	$162.50	$162.50
7 purchase totals =	$990.65		$1,047.6818	$1,047.67	$1,047.65	$1,047.70