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	$114.98	9.398%	$125.7858	$125.79	$125.80	$125.80
Purchase #2	$78.79	12.833%	$88.9011	$88.90	$88.90	$88.90
Purchase #3	$38.70	4.124%	$40.296	$40.30	$40.30	$40.30
Purchase #4	$59.59	6.140%	$63.2488	$63.25	$63.25	$63.20
Purchase #5	$56.42	5.813%	$59.6997	$59.70	$59.70	$59.70
Purchase #6	$91.33	5.746%	$96.5778	$96.58	$96.60	$96.60
Purchase #7	$231.69	7.282%	$248.5617	$248.56	$248.55	$248.60
7 purchase totals =	$671.50		$723.0709	$723.08	$723.10	$723.10