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	$192.80	11.558%	$215.0838	$215.08	$215.10	$215.10
Purchase #2	$199.53	12.512%	$224.4952	$224.50	$224.50	$224.50
Purchase #3	$141.26	4.272%	$147.2946	$147.29	$147.30	$147.30
Purchase #4	$133.89	6.681%	$142.8352	$142.84	$142.85	$142.80
Purchase #5	$185.69	5.489%	$195.8825	$195.88	$195.90	$195.90
Purchase #6	$14.29	12.860%	$16.1277	$16.13	$16.15	$16.10
Purchase #7	$53.39	11.196%	$59.3675	$59.37	$59.35	$59.40
7 purchase totals =	$920.85		$1,001.0865	$1,001.09	$1,001.15	$1,001.10