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	$65.46	12.343%	$73.5397	$73.54	$73.55	$73.50
Purchase #2	$96.47	10.220%	$106.3292	$106.33	$106.35	$106.30
Purchase #3	$143.52	13.525%	$162.9311	$162.93	$162.95	$162.90
Purchase #4	$200.88	6.477%	$213.891	$213.89	$213.90	$213.90
Purchase #5	$156.89	3.604%	$162.5443	$162.54	$162.55	$162.50
Purchase #6	$119.58	5.267%	$125.8783	$125.88	$125.90	$125.90
Purchase #7	$235.59	5.269%	$248.0032	$248.00	$248.00	$248.00
7 purchase totals =	$1,018.39		$1,093.1168	$1,093.11	$1,093.20	$1,093.00