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	$75.25	5.182%	$79.1495	$79.15	$79.15	$79.10
Purchase #2	$19.81	7.404%	$21.2767	$21.28	$21.30	$21.30
Purchase #3	$147.32	4.863%	$154.4842	$154.48	$154.50	$154.50
Purchase #4	$67.45	9.598%	$73.9239	$73.92	$73.90	$73.90
Purchase #5	$56.36	4.796%	$59.063	$59.06	$59.05	$59.10
Purchase #6	$178.59	3.566%	$184.9585	$184.96	$184.95	$185.00
Purchase #7	$154.62	3.395%	$159.8693	$159.87	$159.85	$159.90
7 purchase totals =	$699.40		$732.7251	$732.72	$732.70	$732.80