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	$81.91	4.836%	$85.8712	$85.87	$85.85	$85.90
Purchase #2	$164.64	8.577%	$178.7612	$178.76	$178.75	$178.80
Purchase #3	$59.98	13.227%	$67.9136	$67.91	$67.90	$67.90
Purchase #4	$79.79	9.194%	$87.1259	$87.13	$87.15	$87.10
Purchase #5	$158.64	3.450%	$164.1131	$164.11	$164.10	$164.10
Purchase #6	$146.67	3.268%	$151.4632	$151.46	$151.45	$151.50
Purchase #7	$232.97	5.265%	$245.2359	$245.24	$245.25	$245.20
7 purchase totals =	$924.60		$980.4841	$980.48	$980.45	$980.50