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	$181.89	5.432%	$191.7703	$191.77	$191.75	$191.80
Purchase #2	$16.69	13.337%	$18.9159	$18.92	$18.90	$18.90
Purchase #3	$114.51	5.138%	$120.3935	$120.39	$120.40	$120.40
Purchase #4	$112.34	9.586%	$123.1089	$123.11	$123.10	$123.10
Purchase #5	$179.34	9.566%	$196.4957	$196.50	$196.50	$196.50
Purchase #6	$87.63	12.622%	$98.6907	$98.69	$98.70	$98.70
Purchase #7	$179.97	6.355%	$191.4071	$191.41	$191.40	$191.40
7 purchase totals =	$872.37		$940.7821	$940.79	$940.75	$940.80