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	$47.76	11.708%	$53.3517	$53.35	$53.35	$53.40
Purchase #2	$33.74	11.418%	$37.5924	$37.59	$37.60	$37.60
Purchase #3	$215.86	7.833%	$232.7683	$232.77	$232.75	$232.80
Purchase #4	$176.28	3.710%	$182.82	$182.82	$182.80	$182.80
Purchase #5	$167.60	4.229%	$174.6878	$174.69	$174.70	$174.70
Purchase #6	$238.29	4.267%	$248.4578	$248.46	$248.45	$248.50
Purchase #7	$95.32	6.571%	$101.5835	$101.58	$101.60	$101.60
7 purchase totals =	$974.85		$1,031.2615	$1,031.26	$1,031.25	$1,031.40