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	$40.52	10.738%	$44.871	$44.87	$44.85	$44.90
Purchase #2	$82.39	10.214%	$90.8053	$90.81	$90.80	$90.80
Purchase #3	$242.26	13.686%	$275.4157	$275.42	$275.40	$275.40
Purchase #4	$171.65	9.211%	$187.4607	$187.46	$187.45	$187.50
Purchase #5	$244.53	9.667%	$268.1687	$268.17	$268.15	$268.20
Purchase #6	$162.81	12.786%	$183.6269	$183.63	$183.65	$183.60
Purchase #7	$131.97	10.270%	$145.5233	$145.52	$145.50	$145.50
7 purchase totals =	$1,076.13		$1,195.8716	$1,195.88	$1,195.80	$1,195.90