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	$228.75	6.563%	$243.7629	$243.76	$243.75	$243.80
Purchase #2	$95.44	4.450%	$99.6871	$99.69	$99.70	$99.70
Purchase #3	$14.59	5.529%	$15.3967	$15.40	$15.40	$15.40
Purchase #4	$148.74	6.784%	$158.8305	$158.83	$158.85	$158.80
Purchase #5	$86.60	10.860%	$96.0048	$96.00	$96.00	$96.00
Purchase #6	$172.49	9.526%	$188.9214	$188.92	$188.90	$188.90
Purchase #7	$108.55	13.779%	$123.5071	$123.51	$123.50	$123.50
7 purchase totals =	$855.16		$926.1105	$926.11	$926.10	$926.10