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	$75.32	13.614%	$85.5741	$85.57	$85.55	$85.60
Purchase #2	$236.64	11.419%	$263.6619	$263.66	$263.65	$263.70
Purchase #3	$26.75	6.623%	$28.5217	$28.52	$28.50	$28.50
Purchase #4	$200.46	12.486%	$225.4894	$225.49	$225.50	$225.50
Purchase #5	$79.77	8.282%	$86.3766	$86.38	$86.40	$86.40
Purchase #6	$181.52	5.551%	$191.5962	$191.60	$191.60	$191.60
Purchase #7	$49.27	5.204%	$51.834	$51.83	$51.85	$51.80
7 purchase totals =	$849.73		$933.0539	$933.05	$933.05	$933.10