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	$77.87	7.614%	$83.799	$83.80	$83.80	$83.80
Purchase #2	$153.30	8.584%	$166.4593	$166.46	$166.45	$166.50
Purchase #3	$86.84	13.655%	$98.698	$98.70	$98.70	$98.70
Purchase #4	$152.39	11.745%	$170.2882	$170.29	$170.30	$170.30
Purchase #5	$116.72	3.398%	$120.6861	$120.69	$120.70	$120.70
Purchase #6	$211.64	6.582%	$225.5701	$225.57	$225.55	$225.60
Purchase #7	$57.36	4.420%	$59.8953	$59.90	$59.90	$59.90
7 purchase totals =	$856.12		$925.3960	$925.41	$925.40	$925.50