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	$83.29	7.739%	$89.7358	$89.74	$89.75	$89.70
Purchase #2	$157.66	11.148%	$175.2359	$175.24	$175.25	$175.20
Purchase #3	$128.59	7.761%	$138.5699	$138.57	$138.55	$138.60
Purchase #4	$168.90	9.813%	$185.4742	$185.47	$185.45	$185.50
Purchase #5	$174.85	7.366%	$187.7295	$187.73	$187.75	$187.70
Purchase #6	$8.58	8.843%	$9.3387	$9.34	$9.35	$9.30
Purchase #7	$144.55	8.152%	$156.3337	$156.33	$156.35	$156.30
7 purchase totals =	$866.42		$942.4177	$942.42	$942.45	$942.30