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	$146.63	6.450%	$156.0876	$156.09	$156.10	$156.10
Purchase #2	$56.64	8.339%	$61.3632	$61.36	$61.35	$61.40
Purchase #3	$38.91	10.749%	$43.0924	$43.09	$43.10	$43.10
Purchase #4	$233.44	12.380%	$262.3399	$262.34	$262.35	$262.30
Purchase #5	$104.97	5.640%	$110.8903	$110.89	$110.90	$110.90
Purchase #6	$185.69	5.808%	$196.4749	$196.47	$196.45	$196.50
Purchase #7	$168.85	13.831%	$192.2036	$192.20	$192.20	$192.20
7 purchase totals =	$935.13		$1,022.4519	$1,022.44	$1,022.45	$1,022.50