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	$190.71	9.803%	$209.4053	$209.41	$209.40	$209.40
Purchase #2	$165.76	7.579%	$178.323	$178.32	$178.30	$178.30
Purchase #3	$234.48	13.181%	$265.3868	$265.39	$265.40	$265.40
Purchase #4	$79.77	5.237%	$83.9476	$83.95	$83.95	$83.90
Purchase #5	$142.92	11.320%	$159.0985	$159.10	$159.10	$159.10
Purchase #6	$156.89	3.114%	$161.7756	$161.78	$161.80	$161.80
Purchase #7	$188.29	4.555%	$196.8666	$196.87	$196.85	$196.90
7 purchase totals =	$1,158.82		$1,254.8034	$1,254.82	$1,254.80	$1,254.80