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	$55.60	7.135%	$59.5671	$59.57	$59.55	$59.60
Purchase #2	$230.45	6.536%	$245.5122	$245.51	$245.50	$245.50
Purchase #3	$199.69	9.822%	$219.3036	$219.30	$219.30	$219.30
Purchase #4	$149.31	4.425%	$155.917	$155.92	$155.90	$155.90
Purchase #5	$83.59	7.759%	$90.0757	$90.08	$90.10	$90.10
Purchase #6	$122.28	7.372%	$131.2945	$131.29	$131.30	$131.30
Purchase #7	$187.60	9.338%	$205.1181	$205.12	$205.10	$205.10
7 purchase totals =	$1,028.52		$1,106.7882	$1,106.79	$1,106.75	$1,106.80