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	$41.71	5.114%	$43.843	$43.84	$43.85	$43.80
Purchase #2	$217.43	12.791%	$245.2415	$245.24	$245.25	$245.20
Purchase #3	$124.68	8.173%	$134.8701	$134.87	$134.85	$134.90
Purchase #4	$70.90	3.673%	$73.5042	$73.50	$73.50	$73.50
Purchase #5	$98.80	11.102%	$109.7688	$109.77	$109.75	$109.80
Purchase #6	$102.82	9.466%	$112.5529	$112.55	$112.55	$112.60
Purchase #7	$172.76	9.128%	$188.5295	$188.53	$188.55	$188.50
7 purchase totals =	$829.10		$908.3100	$908.30	$908.30	$908.30