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	$188.98	3.774%	$196.1121	$196.11	$196.10	$196.10
Purchase #2	$237.43	7.740%	$255.8071	$255.81	$255.80	$255.80
Purchase #3	$102.96	11.259%	$114.5523	$114.55	$114.55	$114.60
Purchase #4	$48.43	11.529%	$54.0135	$54.01	$54.00	$54.00
Purchase #5	$48.82	6.333%	$51.9118	$51.91	$51.90	$51.90
Purchase #6	$86.33	12.393%	$97.0289	$97.03	$97.05	$97.00
Purchase #7	$37.49	5.124%	$39.411	$39.41	$39.40	$39.40
7 purchase totals =	$750.44		$808.8367	$808.83	$808.80	$808.80