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	$85.97	7.635%	$92.5338	$92.53	$92.55	$92.50
Purchase #2	$59.42	13.492%	$67.4369	$67.44	$67.45	$67.40
Purchase #3	$41.49	8.417%	$44.9822	$44.98	$45.00	$45.00
Purchase #4	$94.97	3.665%	$98.4507	$98.45	$98.45	$98.50
Purchase #5	$139.31	13.652%	$158.3286	$158.33	$158.35	$158.30
Purchase #6	$120.63	9.251%	$131.7895	$131.79	$131.80	$131.80
Purchase #7	$134.28	12.715%	$151.3537	$151.35	$151.35	$151.40
7 purchase totals =	$676.07		$744.8754	$744.87	$744.95	$744.90