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	$72.69	13.213%	$82.2945	$82.29	$82.30	$82.30
Purchase #2	$160.75	13.508%	$182.4641	$182.46	$182.45	$182.50
Purchase #3	$206.84	3.712%	$214.5179	$214.52	$214.50	$214.50
Purchase #4	$247.96	8.123%	$268.1018	$268.10	$268.10	$268.10
Purchase #5	$106.42	13.683%	$120.9814	$120.98	$121.00	$121.00
Purchase #6	$9.61	7.154%	$10.2975	$10.30	$10.30	$10.30
Purchase #7	$199.30	3.270%	$205.8171	$205.82	$205.80	$205.80
7 purchase totals =	$1,003.57		$1,084.4743	$1,084.47	$1,084.45	$1,084.50