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	$46.87	4.463%	$48.9618	$48.96	$48.95	$49.00
Purchase #2	$35.32	4.711%	$36.9839	$36.98	$37.00	$37.00
Purchase #3	$174.51	11.440%	$194.4739	$194.47	$194.45	$194.50
Purchase #4	$86.63	3.730%	$89.8613	$89.86	$89.85	$89.90
Purchase #5	$165.40	10.574%	$182.8894	$182.89	$182.90	$182.90
Purchase #6	$162.47	5.179%	$170.8843	$170.88	$170.90	$170.90
Purchase #7	$150.79	5.873%	$159.6459	$159.65	$159.65	$159.60
7 purchase totals =	$821.99		$883.7005	$883.69	$883.70	$883.80