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	$139.30	3.412%	$144.0529	$144.05	$144.05	$144.10
Purchase #2	$226.53	12.185%	$254.1327	$254.13	$254.15	$254.10
Purchase #3	$231.47	5.552%	$244.3212	$244.32	$244.30	$244.30
Purchase #4	$98.27	5.421%	$103.5972	$103.60	$103.60	$103.60
Purchase #5	$120.28	12.558%	$135.3848	$135.38	$135.40	$135.40
Purchase #6	$72.77	13.447%	$82.5554	$82.56	$82.55	$82.60
Purchase #7	$152.84	6.588%	$162.9091	$162.91	$162.90	$162.90
7 purchase totals =	$1,041.46		$1,126.9533	$1,126.95	$1,126.95	$1,127.00