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	$168.93	11.515%	$188.3823	$188.38	$188.40	$188.40
Purchase #2	$45.46	11.356%	$50.6224	$50.62	$50.60	$50.60
Purchase #3	$86.45	12.158%	$96.9606	$96.96	$96.95	$97.00
Purchase #4	$17.41	6.165%	$18.4833	$18.48	$18.50	$18.50
Purchase #5	$233.69	4.239%	$243.5961	$243.60	$243.60	$243.60
Purchase #6	$46.63	12.800%	$52.5986	$52.60	$52.60	$52.60
Purchase #7	$110.98	7.766%	$119.5987	$119.60	$119.60	$119.60
7 purchase totals =	$709.55		$770.2420	$770.24	$770.25	$770.30