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	$172.77	12.790%	$194.8673	$194.87	$194.85	$194.90
Purchase #2	$167.44	11.218%	$186.2234	$186.22	$186.20	$186.20
Purchase #3	$95.45	8.756%	$103.8076	$103.81	$103.80	$103.80
Purchase #4	$172.97	6.734%	$184.6178	$184.62	$184.60	$184.60
Purchase #5	$215.84	12.784%	$243.433	$243.43	$243.45	$243.40
Purchase #6	$94.88	11.128%	$105.4382	$105.44	$105.45	$105.40
Purchase #7	$49.54	5.458%	$52.2439	$52.24	$52.25	$52.20
7 purchase totals =	$968.89		$1,070.6312	$1,070.63	$1,070.60	$1,070.50