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	$152.95	12.124%	$171.4937	$171.49	$171.50	$171.50
Purchase #2	$51.91	3.120%	$53.5296	$53.53	$53.55	$53.50
Purchase #3	$226.37	3.304%	$233.8493	$233.85	$233.85	$233.80
Purchase #4	$45.78	3.239%	$47.2628	$47.26	$47.25	$47.30
Purchase #5	$163.90	13.164%	$185.4758	$185.48	$185.50	$185.50
Purchase #6	$220.93	10.681%	$244.5275	$244.53	$244.55	$244.50
Purchase #7	$182.49	11.715%	$203.8687	$203.87	$203.85	$203.90
7 purchase totals =	$1,044.33		$1,140.0074	$1,140.01	$1,140.05	$1,140.00