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	$36.89	3.577%	$38.2096	$38.21	$38.20	$38.20
Purchase #2	$67.68	7.502%	$72.7574	$72.76	$72.75	$72.80
Purchase #3	$126.89	3.275%	$131.0456	$131.05	$131.05	$131.00
Purchase #4	$126.77	4.540%	$132.5254	$132.53	$132.55	$132.50
Purchase #5	$250.66	12.851%	$282.8723	$282.87	$282.85	$282.90
Purchase #6	$92.67	12.660%	$104.402	$104.40	$104.40	$104.40
Purchase #7	$90.73	5.842%	$96.0304	$96.03	$96.05	$96.00
7 purchase totals =	$792.29		$857.8427	$857.85	$857.85	$857.80