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	$184.58	13.683%	$209.8361	$209.84	$209.85	$209.80
Purchase #2	$101.86	12.207%	$114.2941	$114.29	$114.30	$114.30
Purchase #3	$211.56	13.382%	$239.871	$239.87	$239.85	$239.90
Purchase #4	$173.83	9.350%	$190.0831	$190.08	$190.10	$190.10
Purchase #5	$41.31	7.820%	$44.5404	$44.54	$44.55	$44.50
Purchase #6	$98.79	3.431%	$102.1795	$102.18	$102.20	$102.20
Purchase #7	$92.85	7.109%	$99.4507	$99.45	$99.45	$99.50
7 purchase totals =	$904.78		$1,000.2549	$1,000.25	$1,000.30	$1,000.30