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	$144.33	4.694%	$151.1049	$151.10	$151.10	$151.10
Purchase #2	$187.25	12.748%	$211.1206	$211.12	$211.10	$211.10
Purchase #3	$19.35	7.299%	$20.7624	$20.76	$20.75	$20.80
Purchase #4	$184.93	3.595%	$191.5782	$191.58	$191.60	$191.60
Purchase #5	$86.33	6.129%	$91.6212	$91.62	$91.60	$91.60
Purchase #6	$54.89	7.512%	$59.0133	$59.01	$59.00	$59.00
Purchase #7	$167.53	9.755%	$183.8726	$183.87	$183.85	$183.90
7 purchase totals =	$844.61		$909.0732	$909.06	$909.00	$909.10