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	$205.58	5.495%	$216.8766	$216.88	$216.90	$216.90
Purchase #2	$141.69	13.210%	$160.4072	$160.41	$160.40	$160.40
Purchase #3	$209.45	4.775%	$219.4512	$219.45	$219.45	$219.50
Purchase #4	$63.32	6.603%	$67.501	$67.50	$67.50	$67.50
Purchase #5	$154.30	7.561%	$165.9666	$165.97	$165.95	$166.00
Purchase #6	$144.37	6.394%	$153.601	$153.60	$153.60	$153.60
Purchase #7	$219.66	11.791%	$245.5601	$245.56	$245.55	$245.60
7 purchase totals =	$1,138.37		$1,229.3637	$1,229.37	$1,229.35	$1,229.50