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	$175.83	11.630%	$196.279	$196.28	$196.30	$196.30
Purchase #2	$119.84	9.161%	$130.8185	$130.82	$130.80	$130.80
Purchase #3	$110.51	3.214%	$114.0618	$114.06	$114.05	$114.10
Purchase #4	$171.66	12.194%	$192.5922	$192.59	$192.60	$192.60
Purchase #5	$59.80	7.446%	$64.2527	$64.25	$64.25	$64.30
Purchase #6	$150.87	11.771%	$168.6289	$168.63	$168.65	$168.60
Purchase #7	$194.97	7.245%	$209.0956	$209.10	$209.10	$209.10
7 purchase totals =	$983.48		$1,075.7287	$1,075.73	$1,075.75	$1,075.80