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	$163.26	13.776%	$185.7507	$185.75	$185.75	$185.80
Purchase #2	$103.96	7.457%	$111.7123	$111.71	$111.70	$111.70
Purchase #3	$112.70	13.183%	$127.5572	$127.56	$127.55	$127.60
Purchase #4	$194.70	11.858%	$217.7875	$217.79	$217.80	$217.80
Purchase #5	$219.82	12.710%	$247.7591	$247.76	$247.75	$247.80
Purchase #6	$40.75	6.179%	$43.2679	$43.27	$43.25	$43.30
Purchase #7	$13.44	12.637%	$15.1384	$15.14	$15.15	$15.10
7 purchase totals =	$848.63		$948.9731	$948.98	$948.95	$949.10