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	$88.33	4.102%	$91.9533	$91.95	$91.95	$92.00
Purchase #2	$61.58	6.780%	$65.7551	$65.76	$65.75	$65.80
Purchase #3	$131.42	10.267%	$144.9129	$144.91	$144.90	$144.90
Purchase #4	$241.65	3.792%	$250.8134	$250.81	$250.80	$250.80
Purchase #5	$200.40	7.692%	$215.8148	$215.81	$215.80	$215.80
Purchase #6	$169.97	7.405%	$182.5563	$182.56	$182.55	$182.60
Purchase #7	$176.30	7.792%	$190.0373	$190.04	$190.05	$190.00
7 purchase totals =	$1,069.65		$1,141.8431	$1,141.84	$1,141.80	$1,141.90