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	$7.61	4.353%	$7.9413	$7.94	$7.95	$7.90
Purchase #2	$193.46	11.617%	$215.9342	$215.93	$215.95	$215.90
Purchase #3	$142.31	4.596%	$148.8506	$148.85	$148.85	$148.90
Purchase #4	$79.95	11.331%	$89.0091	$89.01	$89.00	$89.00
Purchase #5	$99.75	11.144%	$110.8661	$110.87	$110.85	$110.90
Purchase #6	$67.86	10.157%	$74.7525	$74.75	$74.75	$74.80
Purchase #7	$139.37	7.706%	$150.1099	$150.11	$150.10	$150.10
7 purchase totals =	$730.31		$797.4637	$797.46	$797.45	$797.50