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	$84.90	11.127%	$94.3468	$94.35	$94.35	$94.30
Purchase #2	$80.95	10.651%	$89.572	$89.57	$89.55	$89.60
Purchase #3	$167.76	8.209%	$181.5314	$181.53	$181.55	$181.50
Purchase #4	$77.90	7.685%	$83.8866	$83.89	$83.90	$83.90
Purchase #5	$145.82	3.161%	$150.4294	$150.43	$150.45	$150.40
Purchase #6	$92.86	6.361%	$98.7668	$98.77	$98.75	$98.80
Purchase #7	$104.26	5.146%	$109.6252	$109.63	$109.65	$109.60
7 purchase totals =	$754.45		$808.1582	$808.17	$808.20	$808.10