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	$53.97	9.126%	$58.8953	$58.90	$58.90	$58.90
Purchase #2	$189.86	4.344%	$198.1075	$198.11	$198.10	$198.10
Purchase #3	$75.90	3.593%	$78.6271	$78.63	$78.65	$78.60
Purchase #4	$196.77	4.423%	$205.4731	$205.47	$205.45	$205.50
Purchase #5	$188.46	3.413%	$194.8921	$194.89	$194.90	$194.90
Purchase #6	$67.77	11.617%	$75.6428	$75.64	$75.65	$75.60
Purchase #7	$240.40	12.667%	$270.8515	$270.85	$270.85	$270.90
7 purchase totals =	$1,013.13		$1,082.4894	$1,082.49	$1,082.50	$1,082.50