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	$72.25	11.621%	$80.6462	$80.65	$80.65	$80.60
Purchase #2	$93.61	10.328%	$103.278	$103.28	$103.30	$103.30
Purchase #3	$74.69	11.108%	$82.9866	$82.99	$83.00	$83.00
Purchase #4	$109.46	6.163%	$116.206	$116.21	$116.20	$116.20
Purchase #5	$194.79	7.531%	$209.4596	$209.46	$209.45	$209.50
Purchase #6	$227.64	13.550%	$258.4852	$258.49	$258.50	$258.50
Purchase #7	$131.98	8.687%	$143.4451	$143.45	$143.45	$143.40
7 purchase totals =	$904.42		$994.5067	$994.53	$994.55	$994.50