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	$134.69	4.731%	$141.0622	$141.06	$141.05	$141.10
Purchase #2	$144.77	4.398%	$151.137	$151.14	$151.15	$151.10
Purchase #3	$43.50	9.696%	$47.7178	$47.72	$47.70	$47.70
Purchase #4	$198.89	5.779%	$210.3839	$210.38	$210.40	$210.40
Purchase #5	$92.72	6.855%	$99.076	$99.08	$99.10	$99.10
Purchase #6	$173.45	5.444%	$182.8926	$182.89	$182.90	$182.90
Purchase #7	$200.92	12.586%	$226.2078	$226.21	$226.20	$226.20
7 purchase totals =	$988.94		$1,058.4773	$1,058.48	$1,058.50	$1,058.50