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	$209.32	7.225%	$224.4434	$224.44	$224.45	$224.40
Purchase #2	$132.95	5.486%	$140.2436	$140.24	$140.25	$140.20
Purchase #3	$96.73	13.200%	$109.4984	$109.50	$109.50	$109.50
Purchase #4	$238.38	4.663%	$249.4957	$249.50	$249.50	$249.50
Purchase #5	$59.89	6.682%	$63.8918	$63.89	$63.90	$63.90
Purchase #6	$235.82	4.123%	$245.5429	$245.54	$245.55	$245.50
Purchase #7	$98.51	8.362%	$106.7474	$106.75	$106.75	$106.70
7 purchase totals =	$1,071.60		$1,139.8632	$1,139.86	$1,139.90	$1,139.70