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	$134.59	7.259%	$144.3599	$144.36	$144.35	$144.40
Purchase #2	$243.41	4.105%	$253.402	$253.40	$253.40	$253.40
Purchase #3	$127.72	11.518%	$142.4308	$142.43	$142.45	$142.40
Purchase #4	$246.37	3.170%	$254.1799	$254.18	$254.20	$254.20
Purchase #5	$39.28	7.677%	$42.2955	$42.30	$42.30	$42.30
Purchase #6	$103.61	11.645%	$115.6754	$115.68	$115.70	$115.70
Purchase #7	$113.64	4.650%	$118.9243	$118.92	$118.90	$118.90
7 purchase totals =	$1,008.62		$1,071.2678	$1,071.27	$1,071.30	$1,071.30