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	$48.34	10.137%	$53.2402	$53.24	$53.25	$53.20
Purchase #2	$75.52	9.694%	$82.8409	$82.84	$82.85	$82.80
Purchase #3	$86.91	3.430%	$89.891	$89.89	$89.90	$89.90
Purchase #4	$194.91	7.769%	$210.0526	$210.05	$210.05	$210.10
Purchase #5	$246.98	3.429%	$255.4489	$255.45	$255.45	$255.40
Purchase #6	$102.34	12.366%	$114.9954	$115.00	$115.00	$115.00
Purchase #7	$231.45	3.500%	$239.5508	$239.55	$239.55	$239.60
7 purchase totals =	$986.45		$1,046.0198	$1,046.02	$1,046.05	$1,046.00