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	$82.25	8.349%	$89.1171	$89.12	$89.10	$89.10
Purchase #2	$45.75	12.637%	$51.5314	$51.53	$51.55	$51.50
Purchase #3	$144.92	3.556%	$150.0734	$150.07	$150.05	$150.10
Purchase #4	$229.34	5.739%	$242.5018	$242.50	$242.50	$242.50
Purchase #5	$79.36	4.304%	$82.7757	$82.78	$82.80	$82.80
Purchase #6	$230.26	4.812%	$241.3401	$241.34	$241.35	$241.30
Purchase #7	$166.59	10.309%	$183.7638	$183.76	$183.75	$183.80
7 purchase totals =	$978.47		$1,041.1033	$1,041.10	$1,041.10	$1,041.10