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	$119.60	3.615%	$123.9235	$123.92	$123.90	$123.90
Purchase #2	$127.28	5.869%	$134.7501	$134.75	$134.75	$134.80
Purchase #3	$139.41	9.279%	$152.3459	$152.35	$152.35	$152.30
Purchase #4	$108.60	10.346%	$119.8358	$119.84	$119.85	$119.80
Purchase #5	$125.61	6.140%	$133.3225	$133.32	$133.30	$133.30
Purchase #6	$73.91	8.741%	$80.3705	$80.37	$80.35	$80.40
Purchase #7	$247.64	4.602%	$259.0364	$259.04	$259.05	$259.00
7 purchase totals =	$942.05		$1,003.5847	$1,003.59	$1,003.55	$1,003.50