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	$52.27	6.368%	$55.5986	$55.60	$55.60	$55.60
Purchase #2	$248.68	6.309%	$264.3692	$264.37	$264.35	$264.40
Purchase #3	$18.97	9.131%	$20.7022	$20.70	$20.70	$20.70
Purchase #4	$115.70	7.731%	$124.6448	$124.64	$124.65	$124.60
Purchase #5	$195.47	9.805%	$214.6358	$214.64	$214.65	$214.60
Purchase #6	$131.64	10.597%	$145.5899	$145.59	$145.60	$145.60
Purchase #7	$172.80	13.708%	$196.4874	$196.49	$196.50	$196.50
7 purchase totals =	$935.53		$1,022.0279	$1,022.03	$1,022.05	$1,022.00