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	$141.82	6.418%	$150.922	$150.92	$150.90	$150.90
Purchase #2	$27.40	7.730%	$29.518	$29.52	$29.50	$29.50
Purchase #3	$205.91	8.860%	$224.1536	$224.15	$224.15	$224.20
Purchase #4	$194.56	7.670%	$209.4828	$209.48	$209.50	$209.50
Purchase #5	$174.76	13.242%	$197.9017	$197.90	$197.90	$197.90
Purchase #6	$245.55	8.471%	$266.3505	$266.35	$266.35	$266.40
Purchase #7	$7.89	7.444%	$8.4773	$8.48	$8.50	$8.50
7 purchase totals =	$997.89		$1,086.8059	$1,086.80	$1,086.80	$1,086.90