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	$79.81	3.835%	$82.8707	$82.87	$82.85	$82.90
Purchase #2	$184.32	6.748%	$196.7579	$196.76	$196.75	$196.80
Purchase #3	$130.49	4.490%	$136.349	$136.35	$136.35	$136.30
Purchase #4	$238.69	3.749%	$247.6385	$247.64	$247.65	$247.60
Purchase #5	$249.69	5.745%	$264.0347	$264.03	$264.05	$264.00
Purchase #6	$47.41	9.144%	$51.7452	$51.75	$51.75	$51.70
Purchase #7	$20.75	12.736%	$23.3927	$23.39	$23.40	$23.40
7 purchase totals =	$951.16		$1,002.7887	$1,002.79	$1,002.80	$1,002.70