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	$59.84	11.663%	$66.8191	$66.82	$66.80	$66.80
Purchase #2	$180.77	3.631%	$187.3338	$187.33	$187.35	$187.30
Purchase #3	$162.69	9.558%	$178.2399	$178.24	$178.25	$178.20
Purchase #4	$209.66	6.514%	$223.3173	$223.32	$223.30	$223.30
Purchase #5	$240.47	13.841%	$273.7535	$273.75	$273.75	$273.80
Purchase #6	$68.93	10.714%	$76.3152	$76.32	$76.30	$76.30
Purchase #7	$52.84	3.784%	$54.8395	$54.84	$54.85	$54.80
7 purchase totals =	$975.20		$1,060.6183	$1,060.62	$1,060.60	$1,060.50