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	$161.27	7.642%	$173.5943	$173.59	$173.60	$173.60
Purchase #2	$70.52	11.781%	$78.828	$78.83	$78.85	$78.80
Purchase #3	$148.50	8.323%	$160.8597	$160.86	$160.85	$160.90
Purchase #4	$82.89	4.182%	$86.3565	$86.36	$86.35	$86.40
Purchase #5	$242.35	9.613%	$265.6471	$265.65	$265.65	$265.60
Purchase #6	$46.64	11.605%	$52.0526	$52.05	$52.05	$52.10
Purchase #7	$221.86	9.577%	$243.1075	$243.11	$243.10	$243.10
7 purchase totals =	$974.03		$1,060.4457	$1,060.45	$1,060.45	$1,060.50