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	$65.63	8.360%	$71.1167	$71.12	$71.10	$71.10
Purchase #2	$230.84	4.791%	$241.8995	$241.90	$241.90	$241.90
Purchase #3	$116.69	12.318%	$131.0639	$131.06	$131.05	$131.10
Purchase #4	$155.59	8.244%	$168.4168	$168.42	$168.40	$168.40
Purchase #5	$197.48	7.583%	$212.4549	$212.45	$212.45	$212.50
Purchase #6	$59.90	3.720%	$62.1283	$62.13	$62.15	$62.10
Purchase #7	$103.28	12.121%	$115.7986	$115.80	$115.80	$115.80
7 purchase totals =	$929.41		$1,002.8787	$1,002.88	$1,002.85	$1,002.90