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	$30.69	5.718%	$32.4449	$32.44	$32.45	$32.40
Purchase #2	$124.44	5.524%	$131.3141	$131.31	$131.30	$131.30
Purchase #3	$210.34	5.824%	$222.5902	$222.59	$222.60	$222.60
Purchase #4	$167.98	11.807%	$187.8134	$187.81	$187.80	$187.80
Purchase #5	$134.58	7.486%	$144.6547	$144.65	$144.65	$144.70
Purchase #6	$225.89	10.734%	$250.137	$250.14	$250.15	$250.10
Purchase #7	$140.49	5.652%	$148.4305	$148.43	$148.45	$148.40
7 purchase totals =	$1,034.41		$1,117.3848	$1,117.37	$1,117.40	$1,117.30