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	$172.70	10.807%	$191.3637	$191.36	$191.35	$191.40
Purchase #2	$72.72	4.861%	$76.2549	$76.25	$76.25	$76.30
Purchase #3	$222.50	12.248%	$249.7518	$249.75	$249.75	$249.80
Purchase #4	$215.92	4.209%	$225.0081	$225.01	$225.00	$225.00
Purchase #5	$118.35	7.334%	$127.0298	$127.03	$127.05	$127.00
Purchase #6	$178.62	7.234%	$191.5414	$191.54	$191.55	$191.50
Purchase #7	$39.31	7.741%	$42.353	$42.35	$42.35	$42.40
7 purchase totals =	$1,020.12		$1,103.3027	$1,103.29	$1,103.30	$1,103.40