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	$69.63	8.250%	$75.3745	$75.37	$75.35	$75.40
Purchase #2	$131.63	10.508%	$145.4617	$145.46	$145.45	$145.50
Purchase #3	$46.37	10.234%	$51.1155	$51.12	$51.10	$51.10
Purchase #4	$249.32	13.438%	$282.8236	$282.82	$282.80	$282.80
Purchase #5	$171.30	8.310%	$185.535	$185.54	$185.55	$185.50
Purchase #6	$98.26	8.389%	$106.503	$106.50	$106.50	$106.50
Purchase #7	$244.87	4.185%	$255.1178	$255.12	$255.10	$255.10
7 purchase totals =	$1,011.38		$1,101.9311	$1,101.93	$1,101.85	$1,101.90