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	$61.75	5.499%	$65.1456	$65.15	$65.15	$65.10
Purchase #2	$174.88	9.458%	$191.4202	$191.42	$191.40	$191.40
Purchase #3	$187.32	4.797%	$196.3057	$196.31	$196.30	$196.30
Purchase #4	$240.95	4.210%	$251.094	$251.09	$251.10	$251.10
Purchase #5	$18.78	8.280%	$20.335	$20.34	$20.35	$20.30
Purchase #6	$81.41	8.767%	$88.5472	$88.55	$88.55	$88.50
Purchase #7	$175.88	8.595%	$190.9969	$191.00	$191.00	$191.00
7 purchase totals =	$940.97		$1,003.8446	$1,003.86	$1,003.85	$1,003.70