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	$215.95	3.309%	$223.0958	$223.10	$223.10	$223.10
Purchase #2	$166.78	4.378%	$174.0816	$174.08	$174.10	$174.10
Purchase #3	$19.34	3.807%	$20.0763	$20.08	$20.10	$20.10
Purchase #4	$99.34	4.448%	$103.7586	$103.76	$103.75	$103.80
Purchase #5	$48.65	11.696%	$54.3401	$54.34	$54.35	$54.30
Purchase #6	$142.84	8.206%	$154.5615	$154.56	$154.55	$154.60
Purchase #7	$196.34	13.697%	$223.2327	$223.23	$223.25	$223.20
7 purchase totals =	$889.24		$953.1466	$953.15	$953.20	$953.20