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	$63.33	13.312%	$71.7605	$71.76	$71.75	$71.80
Purchase #2	$121.64	13.301%	$137.8193	$137.82	$137.80	$137.80
Purchase #3	$136.37	6.112%	$144.7049	$144.70	$144.70	$144.70
Purchase #4	$185.27	6.173%	$196.7067	$196.71	$196.70	$196.70
Purchase #5	$171.31	6.533%	$182.5017	$182.50	$182.50	$182.50
Purchase #6	$234.34	11.651%	$261.643	$261.64	$261.65	$261.60
Purchase #7	$167.77	13.835%	$190.981	$190.98	$191.00	$191.00
7 purchase totals =	$1,080.03		$1,186.1171	$1,186.11	$1,186.10	$1,186.10