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	$62.74	3.351%	$64.8424	$64.84	$64.85	$64.80
Purchase #2	$146.53	7.844%	$158.0238	$158.02	$158.00	$158.00
Purchase #3	$145.60	4.476%	$152.1171	$152.12	$152.10	$152.10
Purchase #4	$195.70	13.855%	$222.8142	$222.81	$222.80	$222.80
Purchase #5	$29.70	10.795%	$32.9061	$32.91	$32.90	$32.90
Purchase #6	$86.84	11.415%	$96.7528	$96.75	$96.75	$96.80
Purchase #7	$201.58	6.661%	$215.0072	$215.01	$215.00	$215.00
7 purchase totals =	$868.69		$942.4636	$942.46	$942.40	$942.40