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	$228.32	4.874%	$239.4483	$239.45	$239.45	$239.40
Purchase #2	$39.82	5.152%	$41.8715	$41.87	$41.85	$41.90
Purchase #3	$185.77	10.433%	$205.1514	$205.15	$205.15	$205.20
Purchase #4	$127.83	8.199%	$138.3108	$138.31	$138.30	$138.30
Purchase #5	$52.77	9.743%	$57.9114	$57.91	$57.90	$57.90
Purchase #6	$166.58	11.596%	$185.8966	$185.90	$185.90	$185.90
Purchase #7	$219.31	4.712%	$229.6439	$229.64	$229.65	$229.60
7 purchase totals =	$1,020.40		$1,098.2339	$1,098.23	$1,098.20	$1,098.20