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	$53.32	4.139%	$55.5269	$55.53	$55.55	$55.50
Purchase #2	$164.69	13.121%	$186.299	$186.30	$186.30	$186.30
Purchase #3	$50.99	10.591%	$56.3904	$56.39	$56.40	$56.40
Purchase #4	$138.81	8.331%	$150.3743	$150.37	$150.35	$150.40
Purchase #5	$32.98	8.812%	$35.8862	$35.89	$35.90	$35.90
Purchase #6	$190.25	10.435%	$210.1026	$210.10	$210.10	$210.10
Purchase #7	$163.81	8.828%	$178.2711	$178.27	$178.25	$178.30
7 purchase totals =	$794.85		$872.8505	$872.85	$872.85	$872.90