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	$231.84	3.330%	$239.5603	$239.56	$239.55	$239.60
Purchase #2	$96.63	7.158%	$103.5468	$103.55	$103.55	$103.50
Purchase #3	$208.78	3.725%	$216.5571	$216.56	$216.55	$216.60
Purchase #4	$141.89	4.524%	$148.3091	$148.31	$148.30	$148.30
Purchase #5	$123.92	5.322%	$130.515	$130.52	$130.50	$130.50
Purchase #6	$210.55	11.326%	$234.3969	$234.40	$234.40	$234.40
Purchase #7	$34.99	7.104%	$37.4757	$37.48	$37.50	$37.50
7 purchase totals =	$1,048.60		$1,110.3609	$1,110.38	$1,110.35	$1,110.40