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	$58.62	8.786%	$63.7704	$63.77	$63.75	$63.80
Purchase #2	$127.80	5.506%	$134.8367	$134.84	$134.85	$134.80
Purchase #3	$36.94	4.230%	$38.5026	$38.50	$38.50	$38.50
Purchase #4	$249.80	5.380%	$263.2392	$263.24	$263.25	$263.20
Purchase #5	$222.69	8.791%	$242.2667	$242.27	$242.25	$242.30
Purchase #6	$115.96	9.792%	$127.3148	$127.31	$127.30	$127.30
Purchase #7	$193.61	8.780%	$210.609	$210.61	$210.60	$210.60
7 purchase totals =	$1,005.42		$1,080.5394	$1,080.54	$1,080.50	$1,080.50