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	$145.40	3.353%	$150.2753	$150.28	$150.30	$150.30
Purchase #2	$19.27	9.623%	$21.1244	$21.12	$21.10	$21.10
Purchase #3	$119.53	3.570%	$123.7972	$123.80	$123.80	$123.80
Purchase #4	$20.34	8.548%	$22.0787	$22.08	$22.10	$22.10
Purchase #5	$10.89	7.382%	$11.6939	$11.69	$11.70	$11.70
Purchase #6	$54.91	12.602%	$61.8298	$61.83	$61.85	$61.80
Purchase #7	$73.44	13.199%	$83.1333	$83.13	$83.15	$83.10
7 purchase totals =	$443.78		$473.9326	$473.93	$474.00	$473.90