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	$15.63	4.476%	$16.3296	$16.33	$16.35	$16.30
Purchase #2	$228.39	7.120%	$244.6514	$244.65	$244.65	$244.70
Purchase #3	$130.40	9.569%	$142.878	$142.88	$142.90	$142.90
Purchase #4	$55.83	6.690%	$59.565	$59.57	$59.55	$59.60
Purchase #5	$190.74	9.402%	$208.6734	$208.67	$208.65	$208.70
Purchase #6	$182.46	10.329%	$201.3063	$201.31	$201.30	$201.30
Purchase #7	$239.36	6.168%	$254.1237	$254.12	$254.10	$254.10
7 purchase totals =	$1,042.81		$1,127.5274	$1,127.53	$1,127.50	$1,127.60