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	$171.56	13.269%	$194.3243	$194.32	$194.30	$194.30
Purchase #2	$98.80	4.472%	$103.2183	$103.22	$103.20	$103.20
Purchase #3	$85.45	8.749%	$92.926	$92.93	$92.95	$92.90
Purchase #4	$162.36	13.601%	$184.4426	$184.44	$184.45	$184.40
Purchase #5	$192.39	11.870%	$215.2267	$215.23	$215.25	$215.20
Purchase #6	$207.93	13.301%	$235.5868	$235.59	$235.60	$235.60
Purchase #7	$54.34	12.171%	$60.9537	$60.95	$60.95	$61.00
7 purchase totals =	$972.83		$1,086.6784	$1,086.68	$1,086.70	$1,086.60