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	$79.40	7.721%	$85.5305	$85.53	$85.55	$85.50
Purchase #2	$84.79	13.332%	$96.0942	$96.09	$96.10	$96.10
Purchase #3	$166.60	13.497%	$189.086	$189.09	$189.10	$189.10
Purchase #4	$62.94	12.820%	$71.0089	$71.01	$71.00	$71.00
Purchase #5	$59.75	12.259%	$67.0748	$67.07	$67.05	$67.10
Purchase #6	$98.49	6.306%	$104.7008	$104.70	$104.70	$104.70
Purchase #7	$83.45	7.787%	$89.9483	$89.95	$89.95	$89.90
7 purchase totals =	$635.42		$703.4435	$703.44	$703.45	$703.40