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	$108.78	5.275%	$114.5181	$114.52	$114.50	$114.50
Purchase #2	$225.57	6.539%	$240.32	$240.32	$240.30	$240.30
Purchase #3	$56.61	9.753%	$62.1312	$62.13	$62.15	$62.10
Purchase #4	$150.96	4.573%	$157.8634	$157.86	$157.85	$157.90
Purchase #5	$248.27	8.610%	$269.646	$269.65	$269.65	$269.60
Purchase #6	$30.57	6.828%	$32.6573	$32.66	$32.65	$32.70
Purchase #7	$171.83	5.764%	$181.7343	$181.73	$181.75	$181.70
7 purchase totals =	$992.59		$1,058.8703	$1,058.87	$1,058.85	$1,058.80