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	$165.45	8.391%	$179.3329	$179.33	$179.35	$179.30
Purchase #2	$194.48	5.339%	$204.8633	$204.86	$204.85	$204.90
Purchase #3	$8.44	7.128%	$9.0416	$9.04	$9.05	$9.00
Purchase #4	$70.91	11.253%	$78.8895	$78.89	$78.90	$78.90
Purchase #5	$159.51	12.130%	$178.8586	$178.86	$178.85	$178.90
Purchase #6	$147.70	6.163%	$156.8028	$156.80	$156.80	$156.80
Purchase #7	$174.73	12.351%	$196.3109	$196.31	$196.30	$196.30
7 purchase totals =	$921.22		$1,004.0996	$1,004.09	$1,004.10	$1,004.10