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	$94.44	4.737%	$98.9136	$98.91	$98.90	$98.90
Purchase #2	$57.59	4.430%	$60.1412	$60.14	$60.15	$60.10
Purchase #3	$64.88	12.163%	$72.7714	$72.77	$72.75	$72.80
Purchase #4	$106.76	4.565%	$111.6336	$111.63	$111.65	$111.60
Purchase #5	$113.88	4.256%	$118.7267	$118.73	$118.75	$118.70
Purchase #6	$79.30	13.638%	$90.1149	$90.11	$90.10	$90.10
Purchase #7	$243.78	9.249%	$266.3272	$266.33	$266.35	$266.30
7 purchase totals =	$760.63		$818.6286	$818.62	$818.65	$818.50