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	$237.96	6.671%	$253.8343	$253.83	$253.85	$253.80
Purchase #2	$112.51	13.752%	$127.9824	$127.98	$128.00	$128.00
Purchase #3	$220.93	7.621%	$237.7671	$237.77	$237.75	$237.80
Purchase #4	$219.53	7.475%	$235.9399	$235.94	$235.95	$235.90
Purchase #5	$31.75	3.840%	$32.9692	$32.97	$32.95	$33.00
Purchase #6	$191.66	3.614%	$198.5866	$198.59	$198.60	$198.60
Purchase #7	$38.71	4.853%	$40.5886	$40.59	$40.60	$40.60
7 purchase totals =	$1,053.05		$1,127.6681	$1,127.67	$1,127.70	$1,127.70