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	$156.98	11.304%	$174.725	$174.73	$174.75	$174.70
Purchase #2	$43.32	11.560%	$48.3278	$48.33	$48.35	$48.30
Purchase #3	$107.81	4.747%	$112.9277	$112.93	$112.95	$112.90
Purchase #4	$53.31	7.614%	$57.369	$57.37	$57.35	$57.40
Purchase #5	$89.43	11.650%	$99.8486	$99.85	$99.85	$99.80
Purchase #6	$135.57	6.282%	$144.0865	$144.09	$144.10	$144.10
Purchase #7	$61.85	8.475%	$67.0918	$67.09	$67.10	$67.10
7 purchase totals =	$648.27		$704.3764	$704.39	$704.45	$704.30