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	$79.83	4.831%	$83.6866	$83.69	$83.70	$83.70
Purchase #2	$92.94	8.807%	$101.1252	$101.13	$101.15	$101.10
Purchase #3	$163.87	10.594%	$181.2304	$181.23	$181.25	$181.20
Purchase #4	$35.28	13.541%	$40.0573	$40.06	$40.05	$40.10
Purchase #5	$153.34	3.447%	$158.6256	$158.63	$158.65	$158.60
Purchase #6	$182.46	10.109%	$200.9049	$200.90	$200.90	$200.90
Purchase #7	$249.76	12.646%	$281.3446	$281.34	$281.35	$281.30
7 purchase totals =	$957.48		$1,046.9746	$1,046.98	$1,047.05	$1,046.90