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	$179.88	6.277%	$191.1711	$191.17	$191.15	$191.20
Purchase #2	$14.86	3.445%	$15.3719	$15.37	$15.35	$15.40
Purchase #3	$170.92	7.399%	$183.5664	$183.57	$183.55	$183.60
Purchase #4	$200.49	13.488%	$227.5321	$227.53	$227.55	$227.50
Purchase #5	$54.60	4.193%	$56.8894	$56.89	$56.90	$56.90
Purchase #6	$38.53	6.571%	$41.0618	$41.06	$41.05	$41.10
Purchase #7	$119.62	9.658%	$131.1729	$131.17	$131.15	$131.20
7 purchase totals =	$778.90		$846.7656	$846.76	$846.70	$846.90