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	$204.69	4.700%	$214.3104	$214.31	$214.30	$214.30
Purchase #2	$141.89	3.286%	$146.5525	$146.55	$146.55	$146.60
Purchase #3	$146.36	4.507%	$152.9564	$152.96	$152.95	$153.00
Purchase #4	$113.77	8.670%	$123.6339	$123.63	$123.65	$123.60
Purchase #5	$222.77	3.693%	$230.9969	$231.00	$231.00	$231.00
Purchase #6	$133.67	4.596%	$139.8135	$139.81	$139.80	$139.80
Purchase #7	$90.63	4.535%	$94.7401	$94.74	$94.75	$94.70
7 purchase totals =	$1,053.78		$1,103.0037	$1,103.00	$1,103.00	$1,103.00