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	$239.73	5.834%	$253.7158	$253.72	$253.70	$253.70
Purchase #2	$77.94	10.815%	$86.3692	$86.37	$86.35	$86.40
Purchase #3	$164.77	4.370%	$171.9704	$171.97	$171.95	$172.00
Purchase #4	$91.63	8.521%	$99.4378	$99.44	$99.45	$99.40
Purchase #5	$89.34	10.721%	$98.9181	$98.92	$98.90	$98.90
Purchase #6	$138.89	12.345%	$156.036	$156.04	$156.05	$156.00
Purchase #7	$195.43	8.190%	$211.4357	$211.44	$211.45	$211.40
7 purchase totals =	$997.73		$1,077.8830	$1,077.90	$1,077.85	$1,077.80