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	$86.71	4.488%	$90.6015	$90.60	$90.60	$90.60
Purchase #2	$13.27	10.591%	$14.6754	$14.68	$14.70	$14.70
Purchase #3	$33.94	11.666%	$37.8994	$37.90	$37.90	$37.90
Purchase #4	$193.47	7.288%	$207.5701	$207.57	$207.55	$207.60
Purchase #5	$45.80	3.120%	$47.229	$47.23	$47.25	$47.20
Purchase #6	$50.89	8.233%	$55.0798	$55.08	$55.10	$55.10
Purchase #7	$237.63	5.322%	$250.2767	$250.28	$250.30	$250.30
7 purchase totals =	$661.71		$703.3319	$703.34	$703.40	$703.40