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	$157.86	4.527%	$165.0063	$165.01	$165.00	$165.00
Purchase #2	$205.72	11.772%	$229.9374	$229.94	$229.95	$229.90
Purchase #3	$188.34	4.300%	$196.4386	$196.44	$196.45	$196.40
Purchase #4	$50.83	11.226%	$56.5362	$56.54	$56.55	$56.50
Purchase #5	$101.42	9.787%	$111.346	$111.35	$111.35	$111.30
Purchase #6	$211.88	5.596%	$223.7368	$223.74	$223.75	$223.70
Purchase #7	$155.53	3.318%	$160.6905	$160.69	$160.70	$160.70
7 purchase totals =	$1,071.58		$1,143.6918	$1,143.71	$1,143.75	$1,143.50