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	$98.56	9.156%	$107.5842	$107.58	$107.60	$107.60
Purchase #2	$81.57	9.242%	$89.1087	$89.11	$89.10	$89.10
Purchase #3	$107.59	6.498%	$114.5812	$114.58	$114.60	$114.60
Purchase #4	$82.87	9.712%	$90.9183	$90.92	$90.90	$90.90
Purchase #5	$211.81	6.805%	$226.2237	$226.22	$226.20	$226.20
Purchase #6	$241.48	8.317%	$261.5639	$261.56	$261.55	$261.60
Purchase #7	$196.42	10.206%	$216.4666	$216.47	$216.45	$216.50
7 purchase totals =	$1,020.30		$1,106.4466	$1,106.44	$1,106.40	$1,106.50