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	$74.51	6.110%	$79.0626	$79.06	$79.05	$79.10
Purchase #2	$189.91	3.699%	$196.9348	$196.93	$196.95	$196.90
Purchase #3	$248.59	10.118%	$273.7423	$273.74	$273.75	$273.70
Purchase #4	$98.85	6.744%	$105.5164	$105.52	$105.50	$105.50
Purchase #5	$183.53	13.632%	$208.5488	$208.55	$208.55	$208.50
Purchase #6	$114.92	8.500%	$124.6882	$124.69	$124.70	$124.70
Purchase #7	$24.71	13.608%	$28.0725	$28.07	$28.05	$28.10
7 purchase totals =	$935.02		$1,016.5656	$1,016.56	$1,016.55	$1,016.50