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	$144.41	5.410%	$152.2226	$152.22	$152.20	$152.20
Purchase #2	$74.63	6.336%	$79.3586	$79.36	$79.35	$79.40
Purchase #3	$101.95	6.344%	$108.4177	$108.42	$108.40	$108.40
Purchase #4	$118.29	11.107%	$131.4285	$131.43	$131.45	$131.40
Purchase #5	$242.36	10.752%	$268.4185	$268.42	$268.40	$268.40
Purchase #6	$121.65	8.413%	$131.8844	$131.88	$131.90	$131.90
Purchase #7	$212.40	4.437%	$221.8242	$221.82	$221.80	$221.80
7 purchase totals =	$1,015.69		$1,093.5545	$1,093.55	$1,093.50	$1,093.50