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	$177.54	12.824%	$200.3077	$200.31	$200.30	$200.30
Purchase #2	$85.47	6.840%	$91.3161	$91.32	$91.30	$91.30
Purchase #3	$78.57	9.530%	$86.0577	$86.06	$86.05	$86.10
Purchase #4	$75.59	3.398%	$78.1585	$78.16	$78.15	$78.20
Purchase #5	$27.75	6.145%	$29.4552	$29.46	$29.45	$29.50
Purchase #6	$84.55	3.807%	$87.7688	$87.77	$87.75	$87.80
Purchase #7	$96.92	4.153%	$100.9451	$100.95	$100.95	$100.90
7 purchase totals =	$626.39		$674.0091	$674.03	$673.95	$674.10