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	$66.31	7.818%	$71.4941	$71.49	$71.50	$71.50
Purchase #2	$130.67	8.419%	$141.6711	$141.67	$141.65	$141.70
Purchase #3	$227.71	7.235%	$244.1848	$244.18	$244.20	$244.20
Purchase #4	$97.50	3.298%	$100.7156	$100.72	$100.70	$100.70
Purchase #5	$242.41	10.747%	$268.4618	$268.46	$268.45	$268.50
Purchase #6	$104.45	7.351%	$112.1281	$112.13	$112.15	$112.10
Purchase #7	$78.50	5.471%	$82.7947	$82.79	$82.80	$82.80
7 purchase totals =	$947.55		$1,021.4502	$1,021.44	$1,021.45	$1,021.50