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	$191.55	5.647%	$202.3668	$202.37	$202.35	$202.40
Purchase #2	$138.69	7.353%	$148.8879	$148.89	$148.90	$148.90
Purchase #3	$89.44	11.560%	$99.7793	$99.78	$99.80	$99.80
Purchase #4	$50.38	13.694%	$57.279	$57.28	$57.30	$57.30
Purchase #5	$169.65	10.630%	$187.6838	$187.68	$187.70	$187.70
Purchase #6	$51.47	7.729%	$55.4481	$55.45	$55.45	$55.40
Purchase #7	$57.80	11.401%	$64.3898	$64.39	$64.40	$64.40
7 purchase totals =	$748.98		$815.8347	$815.84	$815.90	$815.90