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	$164.62	5.863%	$174.2717	$174.27	$174.25	$174.30
Purchase #2	$72.27	9.246%	$78.9521	$78.95	$78.95	$79.00
Purchase #3	$241.93	10.135%	$266.4496	$266.45	$266.45	$266.40
Purchase #4	$170.73	12.299%	$191.7281	$191.73	$191.75	$191.70
Purchase #5	$53.93	12.539%	$60.6923	$60.69	$60.70	$60.70
Purchase #6	$131.76	5.807%	$139.4113	$139.41	$139.40	$139.40
Purchase #7	$219.35	6.485%	$233.5748	$233.57	$233.55	$233.60
7 purchase totals =	$1,054.59		$1,145.0799	$1,145.07	$1,145.05	$1,145.10