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	$155.27	7.669%	$167.1777	$167.18	$167.20	$167.20
Purchase #2	$46.64	13.768%	$53.0614	$53.06	$53.05	$53.10
Purchase #3	$44.77	13.109%	$50.6389	$50.64	$50.65	$50.60
Purchase #4	$70.38	3.326%	$72.7208	$72.72	$72.70	$72.70
Purchase #5	$18.88	4.219%	$19.6765	$19.68	$19.70	$19.70
Purchase #6	$166.72	4.531%	$174.2741	$174.27	$174.25	$174.30
Purchase #7	$210.29	8.604%	$228.3834	$228.38	$228.40	$228.40
7 purchase totals =	$712.95		$765.9328	$765.93	$765.95	$766.00