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	$36.78	4.171%	$38.3141	$38.31	$38.30	$38.30
Purchase #2	$5.65	12.309%	$6.3455	$6.35	$6.35	$6.30
Purchase #3	$89.70	11.857%	$100.3357	$100.34	$100.35	$100.30
Purchase #4	$85.40	12.867%	$96.3884	$96.39	$96.40	$96.40
Purchase #5	$55.34	3.203%	$57.1125	$57.11	$57.10	$57.10
Purchase #6	$42.61	10.609%	$47.1305	$47.13	$47.15	$47.10
Purchase #7	$129.66	11.525%	$144.6033	$144.60	$144.60	$144.60
7 purchase totals =	$445.14		$490.2300	$490.23	$490.25	$490.10