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	$40.32	4.371%	$42.0824	$42.08	$42.10	$42.10
Purchase #2	$245.58	5.769%	$259.7475	$259.75	$259.75	$259.70
Purchase #3	$214.96	12.493%	$241.815	$241.82	$241.80	$241.80
Purchase #4	$157.34	7.673%	$169.4127	$169.41	$169.40	$169.40
Purchase #5	$57.44	4.236%	$59.8732	$59.87	$59.85	$59.90
Purchase #6	$110.46	8.175%	$119.4901	$119.49	$119.50	$119.50
Purchase #7	$190.57	5.240%	$200.5559	$200.56	$200.55	$200.60
7 purchase totals =	$1,016.67		$1,092.9768	$1,092.98	$1,092.95	$1,093.00