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	$195.61	10.685%	$216.5109	$216.51	$216.50	$216.50
Purchase #2	$161.85	8.331%	$175.3337	$175.33	$175.35	$175.30
Purchase #3	$203.52	5.829%	$215.3832	$215.38	$215.40	$215.40
Purchase #4	$161.94	7.462%	$174.024	$174.02	$174.00	$174.00
Purchase #5	$149.59	6.453%	$159.243	$159.24	$159.25	$159.20
Purchase #6	$49.80	8.285%	$53.9259	$53.93	$53.95	$53.90
Purchase #7	$74.96	4.121%	$78.0491	$78.05	$78.05	$78.00
7 purchase totals =	$997.27		$1,072.4698	$1,072.46	$1,072.50	$1,072.30