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	$188.56	4.436%	$196.9245	$196.92	$196.90	$196.90
Purchase #2	$69.51	9.479%	$76.0989	$76.10	$76.10	$76.10
Purchase #3	$156.83	3.787%	$162.7692	$162.77	$162.75	$162.80
Purchase #4	$42.56	12.150%	$47.731	$47.73	$47.75	$47.70
Purchase #5	$233.56	5.571%	$246.5716	$246.57	$246.55	$246.60
Purchase #6	$102.58	11.356%	$114.229	$114.23	$114.25	$114.20
Purchase #7	$76.52	6.553%	$81.5344	$81.53	$81.55	$81.50
7 purchase totals =	$870.12		$925.8586	$925.85	$925.85	$925.80