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	$182.80	4.125%	$190.3405	$190.34	$190.35	$190.30
Purchase #2	$38.56	9.863%	$42.3632	$42.36	$42.35	$42.40
Purchase #3	$239.73	6.625%	$255.6121	$255.61	$255.60	$255.60
Purchase #4	$168.31	3.721%	$174.5728	$174.57	$174.55	$174.60
Purchase #5	$128.75	9.598%	$141.1074	$141.11	$141.10	$141.10
Purchase #6	$216.44	6.158%	$229.7684	$229.77	$229.75	$229.80
Purchase #7	$210.32	10.138%	$231.6422	$231.64	$231.65	$231.60
7 purchase totals =	$1,184.91		$1,265.4066	$1,265.40	$1,265.35	$1,265.40