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	$52.98	5.470%	$55.878	$55.88	$55.90	$55.90
Purchase #2	$111.52	12.782%	$125.7745	$125.77	$125.75	$125.80
Purchase #3	$223.70	4.493%	$233.7508	$233.75	$233.75	$233.80
Purchase #4	$39.43	10.756%	$43.6711	$43.67	$43.65	$43.70
Purchase #5	$220.89	5.541%	$233.1295	$233.13	$233.15	$233.10
Purchase #6	$181.98	6.289%	$193.4247	$193.42	$193.40	$193.40
Purchase #7	$214.44	4.204%	$223.4551	$223.46	$223.45	$223.50
7 purchase totals =	$1,044.94		$1,109.0837	$1,109.08	$1,109.05	$1,109.20