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	$31.48	9.385%	$34.4344	$34.43	$34.45	$34.40
Purchase #2	$51.82	10.221%	$57.1165	$57.12	$57.10	$57.10
Purchase #3	$80.62	11.319%	$89.7454	$89.75	$89.75	$89.70
Purchase #4	$95.47	5.300%	$100.5299	$100.53	$100.55	$100.50
Purchase #5	$240.33	6.671%	$256.3624	$256.36	$256.35	$256.40
Purchase #6	$155.95	5.345%	$164.2855	$164.29	$164.30	$164.30
Purchase #7	$73.80	7.571%	$79.3874	$79.39	$79.40	$79.40
7 purchase totals =	$729.47		$781.8615	$781.87	$781.90	$781.80