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	$208.64	6.463%	$222.1244	$222.12	$222.10	$222.10
Purchase #2	$218.86	9.840%	$240.3958	$240.40	$240.40	$240.40
Purchase #3	$49.63	9.311%	$54.251	$54.25	$54.25	$54.30
Purchase #4	$174.49	13.188%	$197.5017	$197.50	$197.50	$197.50
Purchase #5	$172.87	5.778%	$182.8584	$182.86	$182.85	$182.90
Purchase #6	$189.73	8.174%	$205.2385	$205.24	$205.25	$205.20
Purchase #7	$47.27	13.302%	$53.5579	$53.56	$53.55	$53.60
7 purchase totals =	$1,061.49		$1,155.9277	$1,155.93	$1,155.90	$1,156.00