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	$90.62	9.859%	$99.5542	$99.55	$99.55	$99.60
Purchase #2	$215.71	11.365%	$240.2254	$240.23	$240.25	$240.20
Purchase #3	$210.89	9.688%	$231.321	$231.32	$231.30	$231.30
Purchase #4	$130.65	13.729%	$148.5869	$148.59	$148.60	$148.60
Purchase #5	$19.43	4.223%	$20.2505	$20.25	$20.25	$20.30
Purchase #6	$198.78	11.490%	$221.6198	$221.62	$221.60	$221.60
Purchase #7	$227.78	5.137%	$239.4811	$239.48	$239.50	$239.50
7 purchase totals =	$1,093.86		$1,201.0389	$1,201.04	$1,201.05	$1,201.10