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	$95.75	5.759%	$101.2642	$101.26	$101.25	$101.30
Purchase #2	$156.40	11.349%	$174.1498	$174.15	$174.15	$174.10
Purchase #3	$141.51	6.639%	$150.9048	$150.90	$150.90	$150.90
Purchase #4	$244.78	10.180%	$269.6986	$269.70	$269.70	$269.70
Purchase #5	$136.31	8.784%	$148.2835	$148.28	$148.30	$148.30
Purchase #6	$228.89	5.201%	$240.7946	$240.79	$240.80	$240.80
Purchase #7	$55.27	13.340%	$62.643	$62.64	$62.65	$62.60
7 purchase totals =	$1,058.91		$1,147.7385	$1,147.72	$1,147.75	$1,147.70