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	$104.99	4.107%	$109.3019	$109.30	$109.30	$109.30
Purchase #2	$195.32	10.294%	$215.4262	$215.43	$215.45	$215.40
Purchase #3	$232.66	9.809%	$255.4816	$255.48	$255.50	$255.50
Purchase #4	$134.81	10.464%	$148.9165	$148.92	$148.90	$148.90
Purchase #5	$115.29	4.653%	$120.6544	$120.65	$120.65	$120.70
Purchase #6	$76.39	7.819%	$82.3629	$82.36	$82.35	$82.40
Purchase #7	$139.86	9.691%	$153.4138	$153.41	$153.40	$153.40
7 purchase totals =	$999.32		$1,085.5573	$1,085.55	$1,085.55	$1,085.60