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	$173.54	13.453%	$196.8863	$196.89	$196.90	$196.90
Purchase #2	$137.89	7.757%	$148.5861	$148.59	$148.60	$148.60
Purchase #3	$55.75	5.615%	$58.8804	$58.88	$58.90	$58.90
Purchase #4	$239.75	9.532%	$262.603	$262.60	$262.60	$262.60
Purchase #5	$245.84	6.499%	$261.8171	$261.82	$261.80	$261.80
Purchase #6	$165.39	10.853%	$183.3398	$183.34	$183.35	$183.30
Purchase #7	$30.44	5.470%	$32.1051	$32.11	$32.10	$32.10
7 purchase totals =	$1,048.60		$1,144.2178	$1,144.23	$1,144.25	$1,144.20