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	$83.44	9.747%	$91.5729	$91.57	$91.55	$91.60
Purchase #2	$126.88	7.451%	$136.3338	$136.33	$136.35	$136.30
Purchase #3	$153.42	9.650%	$168.225	$168.23	$168.25	$168.20
Purchase #4	$224.57	9.126%	$245.0643	$245.06	$245.05	$245.10
Purchase #5	$200.40	9.709%	$219.8568	$219.86	$219.85	$219.90
Purchase #6	$131.33	10.347%	$144.9187	$144.92	$144.90	$144.90
Purchase #7	$80.35	11.501%	$89.5911	$89.59	$89.60	$89.60
7 purchase totals =	$1,000.39		$1,095.5626	$1,095.56	$1,095.55	$1,095.60