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	$37.70	5.286%	$39.6928	$39.69	$39.70	$39.70
Purchase #2	$110.28	3.620%	$114.2721	$114.27	$114.25	$114.30
Purchase #3	$165.46	7.765%	$178.308	$178.31	$178.30	$178.30
Purchase #4	$131.49	8.284%	$142.3826	$142.38	$142.40	$142.40
Purchase #5	$114.25	5.812%	$120.8902	$120.89	$120.90	$120.90
Purchase #6	$250.34	4.166%	$260.7692	$260.77	$260.75	$260.80
Purchase #7	$154.42	9.420%	$168.9664	$168.97	$168.95	$169.00
7 purchase totals =	$963.94		$1,025.2813	$1,025.28	$1,025.25	$1,025.40