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	$101.89	7.490%	$109.5216	$109.52	$109.50	$109.50
Purchase #2	$60.69	6.332%	$64.5329	$64.53	$64.55	$64.50
Purchase #3	$115.48	6.802%	$123.3349	$123.33	$123.35	$123.30
Purchase #4	$218.65	6.645%	$233.1793	$233.18	$233.20	$233.20
Purchase #5	$88.90	10.341%	$98.0931	$98.09	$98.10	$98.10
Purchase #6	$30.33	9.315%	$33.1552	$33.16	$33.15	$33.20
Purchase #7	$117.66	13.529%	$133.5782	$133.58	$133.60	$133.60
7 purchase totals =	$733.60		$795.3952	$795.39	$795.45	$795.40