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	$240.87	7.151%	$258.0946	$258.09	$258.10	$258.10
Purchase #2	$61.51	3.555%	$63.6967	$63.70	$63.70	$63.70
Purchase #3	$83.88	6.464%	$89.302	$89.30	$89.30	$89.30
Purchase #4	$170.84	10.213%	$188.2879	$188.29	$188.30	$188.30
Purchase #5	$166.90	10.525%	$184.4662	$184.47	$184.45	$184.50
Purchase #6	$179.73	5.120%	$188.9322	$188.93	$188.95	$188.90
Purchase #7	$101.92	9.179%	$111.2752	$111.28	$111.30	$111.30
7 purchase totals =	$1,005.65		$1,084.0548	$1,084.06	$1,084.10	$1,084.10