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	$53.74	4.362%	$56.0841	$56.08	$56.10	$56.10
Purchase #2	$235.88	4.413%	$246.2894	$246.29	$246.30	$246.30
Purchase #3	$70.33	12.265%	$78.956	$78.96	$78.95	$79.00
Purchase #4	$64.59	3.639%	$66.9404	$66.94	$66.95	$66.90
Purchase #5	$184.95	7.617%	$199.0376	$199.04	$199.05	$199.00
Purchase #6	$77.42	11.425%	$86.2652	$86.27	$86.25	$86.30
Purchase #7	$37.65	11.714%	$42.0603	$42.06	$42.05	$42.10
7 purchase totals =	$724.56		$775.6330	$775.64	$775.65	$775.70