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	$65.88	11.804%	$73.6565	$73.66	$73.65	$73.70
Purchase #2	$115.84	6.855%	$123.7808	$123.78	$123.80	$123.80
Purchase #3	$188.43	4.272%	$196.4797	$196.48	$196.50	$196.50
Purchase #4	$112.49	3.209%	$116.0998	$116.10	$116.10	$116.10
Purchase #5	$240.59	11.437%	$268.1063	$268.11	$268.10	$268.10
Purchase #6	$103.91	4.779%	$108.8759	$108.88	$108.90	$108.90
Purchase #7	$76.59	4.842%	$80.2985	$80.30	$80.30	$80.30
7 purchase totals =	$903.73		$967.2975	$967.31	$967.35	$967.40