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	$103.65	4.588%	$108.4055	$108.41	$108.40	$108.40
Purchase #2	$89.98	5.335%	$94.7804	$94.78	$94.80	$94.80
Purchase #3	$68.65	4.134%	$71.488	$71.49	$71.50	$71.50
Purchase #4	$189.96	5.776%	$200.9321	$200.93	$200.95	$200.90
Purchase #5	$167.37	9.255%	$182.8601	$182.86	$182.85	$182.90
Purchase #6	$139.82	12.113%	$156.7564	$156.76	$156.75	$156.80
Purchase #7	$249.65	8.282%	$270.326	$270.33	$270.35	$270.30
7 purchase totals =	$1,009.08		$1,085.5485	$1,085.56	$1,085.60	$1,085.60