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	$242.55	13.727%	$275.8448	$275.84	$275.85	$275.80
Purchase #2	$40.79	7.563%	$43.8749	$43.87	$43.85	$43.90
Purchase #3	$140.82	11.121%	$156.4806	$156.48	$156.50	$156.50
Purchase #4	$51.98	8.197%	$56.2408	$56.24	$56.25	$56.20
Purchase #5	$239.28	4.199%	$249.3274	$249.33	$249.35	$249.30
Purchase #6	$105.35	5.223%	$110.8524	$110.85	$110.85	$110.90
Purchase #7	$241.46	8.315%	$261.5374	$261.54	$261.55	$261.50
7 purchase totals =	$1,062.23		$1,154.1583	$1,154.15	$1,154.20	$1,154.10